Device capable of switching between image display status and a mirror status, and equipment provided therewith

ABSTRACT

There is provided a device capable of switching between a state that displays a high-quality image and a mirror status in which is obtained an easy-to-view reflection image suitable for a person to view his/her own face or figure. An image display portion  1000  that emits image light  3001 , reflective polarization selection means  300  that transmits a first linear polarization component emitted from the image display portion  1000  and reflects a second linear polarization component, whose polarization axis is orthogonal to that of the first linear polarization component, a transmission polarization axis variable portion  400  capable of selecting between one of a state that changes the polarization axis of incident linearly polarized light and a state that does not change the polarization axis of incident linearly polarized light, and a polarization selection member  500  which, of the incident light, absorbs the first linear polarization component and transmits the second linear polarization component, whose polarization axis is orthogonal to that of the first linear polarization component, are disposed in this order. In this case, absorbing polarization selection means  208  is disposed at the image display portion  1000 , and the first linear polarization is emitted as the image light.

TECHNICAL FIELD

[0001] The present invention relates to a display device including amirror function that can switch a display screen to a mirror, aninstrument disposed therewith, and to a mirror including an imagedisplay function that can switch a mirror to an image display screen,and an instrument disposed therewith.

BACKGROUND ART

[0002] As described in, for example, JP-A-11-15392 and JP-A-11-291817,display devices in which a half mirror material is disposed on a frontsurface of an image display member, such as a liquid crystal displaydevice, have been known as display devices capable of switching to amirror status that reflect s outside light (or a mirror disposed with adisplay function) . In these display devices, because outside lightreflected by the half mirror material becomes greater than image lighttransmitted through the half mirror material when a lighting system isturned off or when an image is a dark display, the state becomes amirror status. Conversely, because the image light transmitted throughthe half mirror material becomes greater than the outside lightreflected by the half mirror material when the lighting system is turnedon or when an image is a bright display, the state becomes an imagedisplay status. That is, in these display devices, it is possible tochange the same viewing screen between a mirror status and an imagedisplay status by switching the brightness of the image display memberat the half mirror material rear surface.

[0003] Also, in the republished publication of International PublicationNo. WO99/04315, a liquid crystal display device capable of switchingbetween an open shutter state, in which an image display is viewed, anda closed shutter state, in which the image display is not viewed, isdisclosed. According to this publication, it is written that outsidelight is reflected and becomes “metallic” at the time of the closedshutter state.

[0004] The liquid crystal display device of the republished publicationof WO99/04315 is one in which two liquid crystal display panels, inwhich a liquid crystal layer is injected into a gap between a pair ofsubstrates disposed with electrodes, are stacked, and a polarizing plateis disposed at three places on an upper surface and a lower surface ofthe two stacked liquid crystal display panels, and between the twoliquid crystal display panels. Of these polarizing plates, a reflectivepolarizing plate, which transmits a predetermined linear polarizationand reflects a linear polarization whose polarization axis is orthogonalto that of the predetermined linear polarization, is used as thepolarizing plate disposed between the liquid crystal display panels. Thetransmission polarization axis of the reflective polarizing plate isparallel to the transmission polarization axis of the polarizing plateon the upper surface of the two stacked liquid crystal display panels.Also, a Twist Nematic liquid crystal is used for the liquid crystal ofthe liquid crystal display panel of the upper side (viewer side). Inthis configuration, when a voltage applied to the liquid crystal layerof the liquid crystal display panel of the upper side is small, thelight transmitted through the polarizing plate of the upper surface isstrongly reflected due to reflectance characteristics of the reflectivepolarizing plate, because the polarization direction is rotated 90degrees and the light reaches the reflective polarizing plate when it istransmitted through the liquid crystal layer. Thus, the state becomesthe “metallic” closed shutter state. Conversely, when a voltage appliedto the liquid crystal layer of the liquid crystal display panel of theupper side is large, the polarizing plate of the upper side, the liquidcrystal display panel of the upper side, and the reflective polarizingplate becomes an effectively transparent state and the state thereofbecomes the open shutter state in which the image display of the liquidcrystal display panel of the lower side is viewed. That is, due to thevoltage applied to the liquid crystal display panel of the upper side,it is possible to switch between the closed shutter state, in whichoutside light is reflected and “metallic” is provided, and the openshutter state, in which the display of the liquid crystal display panelof the lower side is viewed.

DISCLOSURE OF THE INVENTION

[0005] Although the above-described conventional display devices arecapable of switching to a mirror-like state that reflects outside light,the mirror-like state is insufficient to use as a mirror with which aperson can view his/her own reflected face or figure. This will bedescribed specifically below.

[0006] Because the display devices of JP-A-11-15392 and JP-A-11-291817use a half mirror, the brightness of the mirror status reflectingoutside light is dependent on the reflectance of the half mirror. Forthis reason, it is necessary to raise the reflectance of the half mirrorin order to make a bright mirror that can be used as a mirror reflectinga person's own face or figure. However, when the reflectance of the halfmirror is raised, the display image becomes dark because the lightamount of the image drops by the amount of light reflected by the halfmirror material at the time the display device is in the image displaystatus. That is, because there is a trade-off relation between thebrightness of the image in the image display status and the brightnessof the mirror in the mirror status, it is difficult to balance both abright image display and a bright mirror. For this reason, it isdifficult to raise the brightness of the mirror status of a displaydevice using a half mirror to the extent that it can be used as a mirrorfor a person to view his/her own reflected face or figure.

[0007] Also, when such a display device using a half mirror is used in abright environment, part of the outside light is reflected by the halfmirror even if the display device is in the image display status. Forthis reason, deterioration of image quality, such as glare of theoutside light and a drop in the contrast ratio of the image resultingfrom reflection of the outside light, arises in the image displaystatus.

[0008] In the display device of the republished publication ofInternational Publication No. WO99/04315, the following problems arisewhen the reflective function of outside light is made to function as amirror for a person to view his/her own reflected face or figure.

[0009] In this display device, when the voltage applied to the liquidcrystal layer of the upper side (the viewer side) liquid crystal panelof the two liquid crystal panels is small, the state becomes the“metallic” closed shutter state. In this case, light made incident fromthe outside is transmitted through the polarizing plate of the uppersurface, is transmitted through the liquid crystal layer of the upperside liquid crystal panel, is reflected by the reflective polarizingplate, and again returns to the outside. Thus, a mirror-like reflectanceis provided. Of the image display light emitted from the lower sideliquid crystal panel, because the polarization axis of light whose stateof polarization is controlled as dark display portion light isorthogonal to the transmission polarization axis of the reflectivepolarizing plate, the light is reflected by the reflective polarizingplate and is not emitted to the outside. However, in reality, because areflective polarizing plate whose reflectance in the directionorthogonal to the transmission polarization axis is completely 100% doesnot exist, part of the dark display portion light is transmitted throughthe reflective polarizing plate. Because the polarization axis of thedark display light transmitted through the reflective polarizing platematches the transmission polarization axis of the polarizing plate ofthe upper surface due to the dark display light being transmittedthrough the liquid crystal layer of the upper side liquid crystal panel,the dark display light is transmitted therethrough and is viewed by theviewer. That is, at the time of the closed shutter mirror status, lightleakage arises from the dark display portion of the image to theoutside.

[0010] Of the image display light emitted from the lower side liquidcrystal panel, because the polarization axis of light whose polarizationstate is controlled as bright display light is parallel to thetransmission polarization axis of the reflective polarizing plate, thelight is transmitted therethrough and passes through the liquid crystallayer of the upper side liquid crystal panel. Because the polarizationaxis is rotated 90 degrees at this time, the polarization axis isorthogonal to the polarizing plate of the upper surface and is absorbedby the polarizing plate of the upper surface. As is commonly known, whenlight passes through a liquid crystal layer whose liquid crystalmolecules are continuously twisted in the thickness direction and isemitted, because the polarization states of light emitted in a diagonaldirection of the liquid crystal layer differ due to the state ofinclination and twist of the liquid crystal molecules in the thicknessdirection, a polarization component that is parallel to the transmissionpolarization axis of the polarizing plate of the upper surface isincluded in the light emitted in the diagonal direction. For thisreason, much light leakage arises from a more diagonal direction thanthe front direction of the display device, whereby the light leakage isviewable to the viewer.

[0011]FIG. 44 shows results in which the present inventors actuallycreated a display device that was virtually the same as the displaydevice of the republished publication of International Publication No.WO99/04315 and measured the leakage of light in the closed shutterstate. The graph of FIG. 44 is data in which image display was conductedin the lower side liquid crystal panel so that a luminance of 450 cd/m²was obtained in the bright display portion when the display device wasimage-displayed in the open shutter state, and in that state, the upperside liquid crystal panel was switched to the closed shutter state andlight leakage from the front surface of the display device was measured.The horizontal axis of FIG. 44 represents positions on the displayportion of the display device and the vertical axis represents luminancevalues in the front direction.

[0012] As shown in FIG. 44, light leakage in the front direction of thedark display portion was a luminance value of 24 to 28 cd/m², and lightleakage in the front direction of the bright display portion was aluminance value of 4 to 5 cd/m². Thus, light leakage in the frontdirection was about seven times larger in the dark display portion thanin the bright display portion. Also, leakage of light at the darkdisplay portion was uneven with respect to position, and colorunevenness was also discernible. It should be noted that the luminancevalue of 4 to 5 cd/m² is a value that is sufficiently visible in a dimenvironment. Also, when observed from a diagonal direction, leakage oflight of 4 to 5 cd/m² or more from the bright display portion was vieweddepending on the direction. In this manner, when the closed shutterstate of the conventional display device is made to function as amirror, the contrast ratio of the reflection image remarkably dropsbecause of the leakage of light. For this reason, it is not sufficientas a mirror reflecting a person's face or figure.

[0013] It should be noted that the birefringence reflective polarizationfilm, in which different birefringence polymer films are alternatinglylaminated, disclosed in, for example, International ApplicationInternational Publication No. WO95/27919 can be used as a reflectivepolarizing plate. This reflective polarizing plate is one that isordinarily disposed between a lighting system (backlight) and apolarizing plate disposed at an undersurface side of a liquid crystalelement and in which extremely high effects are obtained when used forthe purpose of improving the usability of illumination light. However,because leakage of light with respect to a predetermined polarizationbecomes a large problem when realizing mirror capabilities of the kindthat the present inventors aim to realize, sufficient mirrorcapabilities cannot be obtained only with this kind of reflectivepolarizing plate.

[0014] It is an object of the present invention to provide a device thatis capable of switching between a state in which a high-quality image isdisplayed and a mirror status in which is obtained an easy-to-viewreflection image suitable for a person to view his/her own face orfigure.

[0015] In order to attain this object, according to the invention, adevice capable of switching between an image display status and a mirrorstatus of the following configuration is provided.

[0016] That is, there is provided a device capable of switching betweenan image display status and a mirror status, the device including animage display portion that emits image light for displaying a desiredimage and a mirror function portion that is superposed on the imagedisplay portion and is capable of being switched between an imagetransmittance state that transmits the image light and a mirror statusthat reflects outside light,

[0017] the mirror function portion including reflective polarizationselection means, transmission polarization axis variable means, andabsorbing polarization selection means successively disposed from theimage display portion side, with the reflective polarization selectionmeans transmitting a first polarization of a predetermined polarizationaxis and reflecting a second polarization whose polarization axisintersects that of the first polarization, the transmission polarizationaxis variable means being capable of switching between a state thattransmits by changing the incident first polarization to the secondpolarization and a state that transmits without changing thepolarization axis of the incident light, and the absorbing polarizationselection means transmitting one of the first polarization and thesecond polarization and absorbing the other, and

[0018] the image display portion being disposed with image light-usepolarization selection means that transmits the first polarization andabsorbs the second polarization, the image display portion emitting, asthe image light, the first polarization transmitted through the imagelight-use polarization selection means.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is an explanatory drawing for explaining the basicconfiguration and operation of a display device, disposed with afunction for switching to a mirror status, of a first embodiment of theinvention.

[0020]FIG. 2 is an explanatory drawing for explaining the basicconfiguration and operation of the display device, disposed with afunction for switching to a mirror status, of the first embodiment ofthe invention.

[0021]FIG. 3 is a graph showing leakage of light of a bright displayregion in a case where the display device of FIGS. 1 and 2 is in themirror status.

[0022]FIG. 4 is a graph showing leakage of light of a dark displayregion in a case where the display device of FIGS. 1 and 2 is in themirror status.

[0023]FIG. 5 is an explanatory drawing for explaining the basicconfiguration and operation of a display device, disposed with afunction for switching to a mirror status, of a second embodiment of theinvention.

[0024]FIG. 6 is an explanatory drawing for explaining the basicconfiguration and operation of the display device, disposed with afunction for switching to a mirror status, of the second embodiment ofthe invention.

[0025]FIG. 7 is a cross-sectional view showing the configuration of adisplay device of Example 1 of the invention.

[0026]FIG. 8 is a cross-sectional view of respective members configuringthe display device of Example 1 of the invention.

[0027]FIG. 9 are explanatory drawings of directions of axes of therespective members configuring the display device of Example 1 of theinvention.

[0028]FIG. 10 is an explanatory drawing for explaining the operation ofthe display device of Example 1 of the invention.

[0029]FIG. 11 is an explanatory drawing for explaining the operation ofthe display device of Example 1 of the invention.

[0030]FIG. 12 is a graph showing an example of the relationship betweentransmittance and degree of polarization of a common polarizing plate.

[0031]FIG. 13 is a graph showing the relationship between reflectance ofoutside light in an image display status and reflectance in the mirrorstatus and degree of polarization of an absorbing polarization selectionmember 500 pertaining to the display device of Example 1 of theinvention.

[0032]FIG. 14 is a graph showing the relationship between displayluminance in the image display mode and degree of polarization of anabsorbing polarization selection member 208 pertaining to the displaydevice of Example 1 of the invention.

[0033]FIG. 15 is cross-sectional view showing the configuration of adisplay device of Example 2 of the invention.

[0034]FIG. 16 is a cross-sectional view of respective membersconfiguring the display device of Example 2 of the invention.

[0035]FIG. 17 is a cross-sectional view showing an example of theconfiguration of a variable polarization selection member 600 of thedisplay device of Example 2 of the invention.

[0036]FIG. 18 is a cross-sectional view showing an example of theconfiguration of the variable polarization selection member 600 of thedisplay device of Example 2 of the invention.

[0037]FIG. 19 are explanatory drawings of directions of axes of therespective members configuring the display device of Example 2 of theinvention.

[0038]FIG. 20 is an explanatory drawing showing the operation of thedisplay device of Example 2 of the invention.

[0039]FIG. 21 is an explanatory drawing showing the operation of thedisplay device of Example 2 of the invention.

[0040]FIG. 22 is an explanatory drawing showing the schematicconfiguration of a display device of Example 3 of the invention.

[0041]FIG. 23 is a partial cross-sectional view of a transmissive screenof the display device of Example 3 of the invention.

[0042]FIG. 24 is a partial cross-sectional view showing an example of alenticular lens sheet of the display device of Example 3 of theinvention.

[0043]FIG. 25 is a partial perspective view showing an example of thelenticular lens sheet of the display device of Example 3 of theinvention.

[0044]FIG. 26 is a partial cross-sectional view of the transmissivescreen pertaining to the display device of Example 3 of the invention.

[0045]FIG. 27 is a cross-sectional view of respective membersconfiguring a display device of Example 4 of the invention.

[0046]FIG. 28 are explanatory drawings of directions of axes of therespective members configuring the display device of Example 4 of theinvention.

[0047]FIG. 29 is a cross-sectional view of respective membersconfiguring a display device of Example 5 of the invention.

[0048]FIG. 30 are explanatory drawings of directions of axes of therespective members configuring the display device of Example 5 of theinvention.

[0049]FIG. 31 is an explanatory drawing for explaining the operation ofthe display device of Example 5 of the invention.

[0050]FIG. 32 is a cross-sectional view of respective membersconfiguring a display device of Example 6 of the invention.

[0051]FIG. 33 are explanatory drawings of directions of axes of therespective members configuring the display device of Example 6 of theinvention.

[0052]FIG. 34 is an explanatory drawing for explaining the operation ofthe display device of Example 6 of the invention.

[0053]FIG. 35 is an explanatory drawing for explaining the operation ofthe display device of Example 6 of the invention.

[0054]FIG. 36 is a schematic structural diagram for explaining theoperation of the display device of the invention.

[0055]FIG. 37 is a partial cross-sectional view of a display device ofExample 7 of the invention.

[0056] FIGS. 38(a) and 38(b) are top views showing appearances of amobile telephone pertaining to Example 7 of the invention.

[0057]FIG. 39 is a block diagram showing a schematic functionalconfiguration of the mobile telephone pertaining to Example 7 of theinvention.

[0058]FIG. 40 is a top view showing an appearance of a mobile telephonepertaining to Example 8 of the invention.

[0059]FIG. 41 is a partial cross-sectional view showing an example of adetachable mirror function portion pertaining to Example 8 of theinvention.

[0060]FIG. 42 is a block diagram showing a schematic functionalconfiguration of a drive portion of the mirror function portionpertaining to Example 8 of the invention.

[0061]FIG. 43 is a partial cross-sectional view showing an example of adisplay device of Example 9 of the invention.

[0062]FIG. 44 is a graph showing leakage of light in a shutter state ofa conventional display device.

BEST MODES FOR IMPLEMENTING THE INVENTION

[0063] A device of an embodiment of the invention will be describedbelow.

[0064] In the present embodiment, a device capable of switching betweenan image display status and a mirror status (i.e., a display devicedisposed with a mirror function or a mirror disposed with a displayfunction) is provided. In the mirror status, the device prevents lightleakage of image display light and a reflection image that is bright andhas a high contrast ratio can be obtained. Thus, in the case of themirror status, the device of the present embodiment is suited for aperson to view his/her own reflected face or figure. It is commonlythought that the way people view faces is dependent upon physicalquantities, such as area size, luminance, and contrast ratio (luminancecontrast), and it has been experimentally confirmed that, the larger thecontrast ratio (luminance contrast) is, the higher the evaluation thatsomething is easy to see is (Shino Okada and Ryuji Sato, “Hito no kao nomiekata ni taisuru hyokaho no kochiku ni kansuru kiso kento” (“Basicconsiderations relating to the construction of evaluation methods withrespect to the way people view faces”), Shomei Gakkaishi (“Journal ofLight & Visual Environment”), Vol. 84, No. 11, pp. 809-814). Also, withthe device of the present embodiment, in the image display status, thereis little deterioration of image quality, such as a drop in the contrastratio or glare of outside light, even in a bright environment, and abright image is obtained.

[0065] A display device disposed with a function for switching to amirror status of the embodiments of the invention will be describedbelow with reference to FIGS. 1 to 6.

[0066] (First Embodiment)

[0067] First, the basic configuration and operation of a display devicedisposed with a function for switching to a mirror status of a firstembodiment will be described using FIGS. 1 and 2.

[0068] As shown in FIG. 1, the display device of the first embodimentincludes an image display portion 1000, a reflective polarizationselection member 300, a transmission polarization axis variable portion400, and an absorbing polarization selection member 500, which aresuccessively disposed. The image display portion 1000 includes anabsorbing polarization selection member 208 that transmits a linearpolarization component of a predetermined direction and absorbs a linearpolarization component of a direction orthogonal thereto, and theabsorbing polarization selection member 208 is disposed at thereflective polarization selection member 300 side. In the presentembodiment, the image display portion 1000 includes two absorbingpolarization selection members that sandwich a lighting system, a liquidcrystal layer, and a liquid crystal layer. Of the two absorbingpolarization selection members, the one at the emission side is theabsorbing polarization selection member 208. A voltage applied to theliquid crystal layers is changed between a bright display region and adark display region, the linear polarization transmitted through theabsorbing polarization selection member 208 is emitted from the brightdisplay region, light is absorbed by the absorbing polarizationselection member 208 at the dark display region, and the light is notemitted. Thus, it is a configuration that displays an image.Accordingly, image light (bright display light) emitted from the imagedisplay portion 1000 is a linear polarization including a polarizationaxis that matches a transmission polarization axis of the absorbingpolarization selection member 208. A linear polarization including apolarization axis of a direction that is the same as that of apolarization axis of the image light will be referred to below as a“first linear polarization”. A linear polarization of a direction inwhich a polarization axis thereof is orthogonal to that of the firstlinear polarization will be referred to as a “second linearpolarization”.

[0069] The reflective polarization selection member 300 is a member thattransmits a linear polarization component of a predetermined directionand reflects a linear polarization component orthogonal thereto. Here,the reflective polarization selection member 300 is disposed at anorientation that transmits the first linear polarization component andreflects the second linear polarization component.

[0070] The transmission polarization axis variable portion 400 is anelement including a structure that can select, by electrical switching,between a state that changes the polarization axis when incidentlinearly polarized light is transmitted therethrough and a state thatdoes not change the polarization axis. In the present embodiment, aliquid crystal element, which includes a liquid crystal layer 407 andtransparent electrodes 403 and 406 for applying a voltage to the liquidcrystal layer 407, is used as the transmission polarization axisvariable portion 400. A switching switch 813, which switches the voltageon and off, is connected to the transparent electrode 403. When thevoltage applied to the liquid crystal layer 407 is switched off by theswitching switch 813, the liquid crystal layer 407 is in a state thatchanges the polarization axis of an incident linear polarization, andwhen the voltage is switched on, the liquid crystal layer 407 is in astate that does not change the polarization axis. In the presentembodiment, the liquid crystal layer 407 is a so-called Twist Nematic(TN) liquid crystal configured so that, when the voltage is OFF, longaxes of liquid crystal molecules 407 a are continuously twisted 90°between the transparent electrode 403 and the transparent electrode 406.The orientation direction of the liquid crystal layer 407 is set to adirection in which the first linear polarization made incident from thereflective polarizationselectionmember300 side is changed to the secondlinear polarization. When the voltage is on, the liquid crystalmolecules 407 a of the liquid crystal layer 407 stand perpendicular tothe transparent electrodes 403 and 406, as shown in FIG. 2, and become astate that does not change the polarization axis of the incident light.

[0071] The absorbing polarization selection member 500 is a member thattransmits a linear polarization component of a predetermined directionand absorbs a linear polarization component of a direction orthogonalthereto. Here, the absorbing polarization selection member 500 isdisposed so as to absorb the first linear polarization component andtransmit the second linear polarization component of the incident light.

[0072] It should be noted that a viewer views the present display devicefrom the absorbing polarization selection member 500 side (the left sideof the page in FIG. 1).

[0073] Next, the operation of the display device of the first embodimentwill be described using FIGS. 1 and 2.

[0074] As shown in FIG. 1, when the display device of the presentembodiment is used in the image display status, the switching switch 813is switched off and the display device is set so that the liquid crystalmolecules 407 a of the liquid crystal layer 407 of the transmissionpolarization axis variable portion 400 are in a 90° twisted state. Inthis state, image light (bright display light) 3001 of a desired displayis emitted from the image display portion 1000. Because the image. light3001 is light that passes through the absorbing polarization selectionmember 208 of the image display portion 1000, it is the first linearpolarization. Accordingly, the polarization axis of the image light 3001matches the transmission polarization axis of the reflectivepolarization selection member 300, and the image light 3001 istransmitted through the reflective polarization selection member 300 andis made incident at the transmission polarization axis variable portion400. As mentioned above, because the liquid crystal layer 407 of thetransmission polarization axis variable portion 400 is set to an OFFstate, the image light 3001 of the incident first linear polarizationbecomes the second linear polarization due to its polarization axisbeing rotated along the twist of the liquid crystal molecules 407 a, andis emitted. Because the polarization axis of the image light 3001 thathas become the second linear polarization matches the transmissionpolarization axis of the absorbing polarization selection member 500,the image light 3001 is transmitted therethrough and is viewable to theviewer.

[0075] On the other hand, because outside light 3002 that is madeincident at the display device from the viewer side when the displaydevice is in the image display status is non-polarized light, the firstlinear polarization component is absorbed when it is transmitted throughthe absorbing polarization selection member 500, and only the secondlinear polarization component is transmitted. The outside light 3002 ofthe second linear polarization that is transmitted through the absorbingpolarization selection member 500 is changed from the second linearpolarization to the first linear polarization when it is transmittedthrough the transmission polarization axis variable portion 400. Thus,because the polarization axis thereof matches the transmissionpolarization axis of the reflective polarization selection member 300,it is transmitted and made incident at the image display portion 1000without being reflected by the reflective polarization selection member.Because the polarization axis of the outside light 3002 of the incidentfirst linear polarization matches the transmission polarization axis ofthe absorbing polarization selection member 208, the outside light 3002is transmitted through the absorbing polarization selection member 208and made incident at the liquid crystal layer of the image displayportion 1000. At this time, the light made incident at the dark displayregion is absorbed by the absorbing polarization selection memberdisposed nearer to the lighting system side than the liquid crystallayer. Accordingly, it does not return to the viewer side. Also, thelight made incident at the bright display region is also transmittedthrough the absorbing polarization selection member at a light sourceside and reaches the lighting system. Although part of the lightreaching the lighting system is reflected thereby, the reflected lightis substantially no different from the illumination light and becomespart of the illumination light, whereby outside light that causes imagequality to deteriorate is not reflected. That is, in the display deviceof the present embodiment, even if outside light is made incident in theimage display status, there is virtually no reflection of outside lightthat causes image quality to deteriorate.

[0076] In this manner, with the display device of the presentembodiment, a bright image is obtained because the image light 3001proceeds toward the viewer with virtually no loss in the image displaystatus. Because the outside light 3002 is virtually not reflected in thedisplay device, there is virtually no deterioration of image qualityresulting from reflection of the outside light, such as a glare and adrop in the contrast ratio.

[0077] Next, a case in which the display device of the presentembodiment is switched to the mirror status and used will be described.In this case, as shown in FIG. 2, the switching switch 813 is switchedon, and the liquid crystal molecules 407 a of the liquid crystal layer407 of the transmission polarization axis variable portion 400 are setto a state in which they are made to stand.

[0078] At this time, although the outside light 3002 proceeding towardthe display device from the viewer side is non-polarized light, when itis transmitted through the absorbing polarization selection member 500,the first linear polarization component is absorbed and only the secondlinear polarization component is transmitted and made incident at thetransmission polarization axis variable portion 400. With respect to thetransmission polarization axis variable portion 400, because the liquidcrystal molecules 407 a of the liquid crystal layer 407 are in astanding state, the incident outside light 3002 is transmitted throughthe transmission polarization axis variable portion 400 as the secondlinear polarization, without its polarization state being changed, andreaches the reflective polarization selection member 300. Because thereflection polarization axis of the reflective polarization selectionmember 300 matches the polarization axis of the second linearpolarization, the outside light 3002 is reflected by the reflectivepolarization selection member 300. The outside light 3002 reflected bythe reflective polarization selection member 300 is again made incidentat the transmission polarization axis variable portion 400, istransmitted therethrough as the second linearly polarized light,emitted, further transmitted through the absorbing polarizationselection member 400, and proceeds toward the viewer. Thus, a reflectionimage of the outside light 3002 is obtained, and the mirror status isrealized.

[0079] At the time of the mirror status, because the image light (brightdisplay light) 3001 emitted from the image display portion 1000 is thefirst linear polarization transmitted through the absorbing polarizationselection member 208, it is transmitted through the reflectivepolarization selection member 300 and made incident at the transmissionpolarization axis variable portion 400. Because the transmissionpolarization axis variable portion 400 is in an ON state, thepolarization state of the image light 3001 is not changed, and the imagelight 3001 is transmitted therethrough as the first linear polarizationand made incident at the absorbing polarization selection member 500.Because the first linear polarization matches the absorptionpolarization axis of the absorbing polarization selection member 500, itis absorbed by the absorbing polarization selection member 500 and isnot viewable to the viewer.

[0080] In other words, in the case of the mirror status, the light fromthe image display member does not reach the viewer, and the outsidelight 3002 made incident at the display device from the surrounding areafunctions as a bright mirror because half the light of the non-polarizedlight is ideally reflected by the reflective polarization selectionmember 300 and proceeds toward the viewer side.

[0081] It should be noted that, in the case of the mirror status, thedisplay device of the present embodiment can greatly reduce lightleakage in comparison to the display device of the republishedpublication of International Publication No. WO99/04315. InInternational Publication No. WO99/04315, light leakage from the darkdisplay portion stemming from the reflective capability of thereflective polarizing plate was a problem in the mirror status. However,in the display device of the present embodiment, because the imagedisplay portion 1000 is disposed with the absorbing polarizationselection member 208 and absorbs the illumination light of the darkdisplay region, light does not reach the reflective polarizationselection member 300 at the dark display region. For this reason,regardless of the capability of the reflective polarization selectionmember 300, light leakage from the dark display region is virtually notviewable.

[0082] Also, the display device of the present embodiment has aconfiguration in which the transmission polarization axis variableportion 400 is switched on and the liquid crystal molecules 407 a aremade to stand at the time of the mirror status. Usually, with a nematicliquid crystal, there is less offset of the polarization axis of lightemitted in a diagonal direction when the voltage is on and the liquidcrystal molecules are made to stand than when the voltage is off and theliquid crystal molecules are twisted. For this reason, with the displaydevice of the present embodiment, the effect is obtained that there islittle light leakage in a diagonal direction of the image light (brightdisplay light) 3001 in the mirror status in comparison to the displaydevice of the configuration in which the voltage is switched off in themirror status described in the conventional art.

[0083] Leakage of light from the image display portion 1000 in themirror status will be specifically described using the graphs of FIGS. 3and 4. FIG. 3 shows, in luminance values, the magnitude of leakage oflight at the bright display region, and FIG. 4 shows, in luminancevalues, the magnitude of leakage of light at the dark display region.These graphs are data in a case in which bright display at a luminanceof 450 cd/m² was conducted when the display device was in the imagedisplay status. The horizontal axes represent positions on the displayportion of the display device, and the vertical axes represent luminancevalues in a front direction, i.e., in a direction perpendicular to thescreen. FIGS. 3 and 4 also show respective light leakage inconfigurations using an A-type polarizing plate, a B-type polarizingplate, and a C-type polarizing plate as the absorbing polarizationselection member. 208 of the image display portion 1000, and lightleakage in a device in which the absorbing polarization selection member208 was removed from the image display portion 1000 and in which otherconfigurations were the same as those of the image device of the presentembodiment. It should be noted that, even with the configuration inwhich the absorbing polarization selection member 208 had been removed,an image of an ordinary level could be displayed in the image displaystatus. Details of the A- , B- , and C-type polarizing plates will bedescribed later.

[0084] As shown in FIG. 3, in the bright display region in the mirrorstatus, leakage of light in the display device of the present embodimentusing the absorbing polarization selection member 208 was suppressed toabout half the leakage of light in the device in which there was noabsorbing polarization selection member 208. For this reason, a mirrorthat reflected a reflection image in which the contrast ratio was highcould be realized with the display device of the present embodiment.Also, as shown in FIG. 4, in the dark display region in the mirrorstatus, because there was virtually no leakage of light in the displaydevice of the present embodiment using the absorbing polarizationselection member 208, a mirror reflecting an easy-to-view reflectionimage in which the contrast ratio was higher could be realized. On theother hand, as shown in FIG. 4, a lot of light leakage arose in the darkdisplay region with the display device that did not use the absorbingpolarization selection member 208.

[0085] These facts show that, by switching the display of the imagedisplay portion 1000 to a dark display at the time of the mirror status,a mirror having good visibility could be realized with the displaydevice of the present embodiment. This is in contrast to the fact thatthere was more leakage of light in the dark display portion than in thebright display portion in the display device of the configuration notdisposed with the absorbing polarization selection member (polarizingplate) 208 showing light leakage in FIGS. 3 and 4 and in theconventional display device showing light leakage in FIG. 44.

[0086] Accordingly, in the present embodiment, in a case where theentire screen is switched to the mirror status, the entire image displayportion 1000 is switched to the dark display or the entire lightingsystem of the image display portion 1000 is switched to a non-emittingstate. Also, in a case where the voltage is switched on only at apartial region of the transmission polarization axis variable portion400 and only part of the screen is switched to the mirror status, theimage display portion 1000 of the region overlapping with the regionswitched to the mirror status is switched to the dark display or thenon-emitting state. Thus, light leakage from the portion of the mirrorstatus is reduced, and a reflection image having a high contrast ratiocan be reflected.

[0087] Specifically, if the switching switch 813 is switched on in orderto switch to the mirror status, the display device can have aconfiguration in which a circuit that switches the liquid crystalelement of the image display portion 1000 to the dark display inconjunction with the switching switch 813 is disposed, or in which acircuit that turns off the lighting system at the rear side of theliquid crystal element of the image display portion 1000 is disposed. Ina case where the lighting system is turned off in the mirror status,reduction of the power consumption of the display device becomespossible. It should be noted that, in a case where only part of thescreen is switched to the mirror status and an image is displayed on theremaining portion, it is preferable to switch the image display portion1000 of the region overlapping with the region switched to the mirrorstatus to the dark display because the display of the image displayregion becomes dark when the lighting system at the rear side of theliquid crystal element is turned off. Thus, it becomes possible torealize a mirror status that can realize a reflection image having ahigh contrast ratio and, at the same time, realize a bright imagedisplay on the same screen.

[0088] In addition to the display portion using the liquid crystalelement, a self-luminous display portion, such as an organicelectroluminescence (EL: electroluminescence) element, can also be usedas the image display portion 1000. The absorbing polarization selectionmember 208 is disposed at a position facing the EL element reflectivepolarization selection member 300. When an EL element is used, leakageof light can, in principle, be eliminated by stopping the emission oflight itself of the EL element in conjunction with switching to themirror status and switching the display device to the dark displaystate. Thus, a high-definition mirror status, in which a reflectionimage having a high contrast ratio is obtained, can be realized, andreduction of the power consumption of the display device becomespossible.

[0089] The display device of the present embodiment can also be madeinto a projection display device by using a disvoltage lamp, such as ametal halide lamp, as the light source of the lighting system of theimage display portion 1000 and combining this with the liquid crystalelement. In this case, because the disvoltage lamp cannot be quicklyturned on and off, it is preferable to configure the device to reducelight leakage by switching the display of the image display portion 1000to the dark display in conjunction with switching to the mirror status.

[0090] It should be noted that, although a member whose transmissionpolarization axis is parallel to the polarization axis of the firstlinear polarization and whose absorption polarization axis is parallelto the polarization axis of the second linear polarization was used inthe first embodiment as the absorbing polarization selection member 500,as shown in FIGS. 1 and 2, the present invention is not limited thereto.A member whose transmission polarization axis is parallel to thepolarization axis of the second linear polarization and whose absorptionpolarization axis is parallel to the polarization axis of the firstlinear polarization can also be used. In this case, the display deviceis switched to an image transmittance state by switching thetransmission polarization axis variable portion 400 to a state thattransmits without changing the incident polarization axis (state inwhich the voltage is on), and the display device is switched to themirror status by switching the transmission polarization axis variablemember 400 to a state that changes the first polarization to the secondpolarization (state in which the voltage is off).

[0091] (Second Embodiment)

[0092] Next, the basic configuration and operation of a display devicedisposed with a function for switching to a mirror status of a secondembodiment of the invention will be described using FIGS. 5 and 6.

[0093] The display device of the second embodiment is one in which theabsorbing polarization selection member 500 of the display device ofFIGS. 1 and 2 of the first embodiment is replaced with a combination ofa reflective polarization selection member 301 and a variablepolarization selection member 600. Because other configurations are thesame as those of the display device of the first embodiment, the samereference numerals will be given to the same parts and detaileddescription thereof will be omitted.

[0094] The reflective polarization selection member 301 is disposed at aposition facing the transmission polarization axis variable portion 400,and the variable polarization selection member 600 is disposed furthertoward the viewer side than the reflective polarization selection member301. The reflective polarization selection member 301 has aconfiguration that reflects the first linear polarization component andtransmits the second linear polarization component. The variablepolarization selection member 600 has a configuration in which it ispossible to select between a state that, of the incident light, absorbsthe first linear polarization component and transmits the second linearpolarization component and a state that transmits all linearpolarization components.

[0095] The display device of the second embodiment is configured so thatswitching between the image display status and the mirror status isaccomplished by control of the polarization state by the transmissionpolarization axis variable portion 400 and by control of the absorptionor transmission of the polarization by the variable polarizationselection member 600. It should be noted that a viewer views the displaydevice from the variable polarization selection member 600 side.

[0096] Here, a member including a guest host liquid crystal layer 607,transparent electrodes 603 and 606 that apply a voltage to the liquidcrystal layer 607, and a switching switch 600 a is used for the variablepolarization selection member 600. When the switching switch 600 a isoff, as shown in FIG. 5, the liquid crystal layer 607 is orientated sothat long axes of liquid crystal molecules 607 a of the liquid crystallayer 607 are parallel to the first linear polarization. Thus, in an OFFstate, the variable polarization selection member 600 absorbs the firstlinear polarization component and transmits the second linearpolarization component, whose polarization axis is orthogonal to thepolarization axis of the first linear polarization component. When theswitching switch 600 a is on, as shown in FIG. 6, the liquid crystalmolecules 607 a become perpendicular to the transparent electrodes 603and 606, whereby the variable polarization selection member 600transmits all polarization components.

[0097] The operation of the display device of the second embodiment whenthe display device is in the image display status will be describedusing FIG. 5. When the display device is switched to the image displaystatus, the switching switch 813 is switched off, the transmissionpolarization axis variable portion 400 is switched to an OFF state and,in conjunction therewith, the switching switch 600 a is switched off,and the variable polarization selection member 600 is switched to an OFFstate.

[0098] The image light 3001 that is emitted from the image displayportion 1000 is transmitted through the reflective polarizationselection member 300 and made incident at the transmission polarizationaxis variable portion 400. Because the transmission polarization axisvariable portion 400 is in the OFF state at this time, the image light3001 passing therethrough is changed from the first linear polarizationto the second linear polarization. Because the image light 3001transmitted through the transmission polarization axis variable portion400 becomes the second linear polarization, the polarization axisthereof matches the transmission polarization ax is of the reflectivepolarization selection member 301, and the image light 3001 istransmitted therethrough. Moreover, because it also matches thetransmission polarization axis of the variable polarization selectionmember 600 in the OFF state, the image light 3001 is also transmittedtherethrough and is viewable to the viewer.

[0099] Although the outside light 3002 that is made incident at thedisplay device in the image display status from the viewer side isnon-polarized light, because the variable polarization selection member600 is in the OFF state, the first linear polarization component, whichmatches the absorption polarization axis of the variable polarizationselection member, is absorbed, and only the second linear polarizationcomponent, which matches the transmission polarization axis, istransmitted. When the outside light 3002 of the second linearpolarization transmitted through the variable polarization selectionmember 600 is transmitted through the reflective polarization selectionmember 300 and transmitted through the transmission polarization axisvariable portion 400, it is changed from the second linearly polarizedlight to the first linearly polarized light, transmitted through thefirst reflective polarization selection member 300, and made incident atthe liquid crystal layer of the image display portion 1000. At thistime, as described in the first embodiment, the light made incident atthe dark display region is absorbed by the absorbing polarizationselection member disposed further toward the lighting system side thanthe liquid crystal layer. Thus, it does not return to the viewer side.Although the light made incident at the bright display region is alsotransmitted through the absorption polarization selection member of thelight source side, reaches the lighting system, and part of the light isreflected, the reflected light is substantially no different from theillumination light and becomes part of the illumination light. That is,in the display device of the present embodiment, at the time of theimage display status, there is virtually no reflection of outside lightthat causes image quality to deteriorate, even if the outside light ismade incident.

[0100] Therefore, in the image display status, a bright image can beobtained because the image light 3001 proceeds toward the viewer withvirtually no loss. Also, because the outside light 3002 is virtually notreflected in the display device, deterioration of image quality, such asa glare of outside light and a drop in the contrast ratio, does notarise.

[0101] Next, the operation of the display device of the secondembodiment when the display device is in the mirror status will bedescribed using FIG. 6. In the case of the mirror status, the switchingswitch 813 and the switching switch 600 a are switched on at the sametime, and the transmission polarization axis variable portion 400 andthe variable polarization selection member 600 are switched to an ONstate.

[0102] In the case of the mirror status, all of the polarizationcomponents of the outside light 3002 that is made incident at thedisplay device from the viewer side are transmitted through the variablepolarization selection member 600, as shown in FIG. 6. The outside light3002 transmitted through the variable polarization selection member 600is made incident at the reflective polarization selection member 301. Ofthe outside light 3002 made incident at the reflective polarizationselection member 301, the second linear polarization component istransmitted through the reflective polarization selection member 301,and the first linear polarization component is reflected by thereflective polarization selection member 301, is again transmittedthrough the variable polarization selection member 600, and proceedstoward the viewer side. The second linear polarization componenttransmitted through the reflective polarization selection member 301 istransmitted through the transmission polarization axis variable portion400 without its polarization axis being changed, is reflected by thereflective polarization selection member 300, is again transmittedthrough the transmission polarization axis variable portion 400, throughthe reflective polarization selection member 301, and through thevariable polarization selection member 600, and proceeds toward theviewer side.

[0103] In this manner, in the display device of the second embodiment,most of the polarization components of the incident outside light 3002are reflected by the reflective polarization selection member 300 andthe reflective polarization selection member 301. Therefore, a mirrorstatus in which is obtained an extremely bright reflection image can beobtained.

[0104] In the case of the mirror status, because the image light (brightdisplay light) 3001 emitted from the image display portion 1000 passesthrough the absorbing polarization selection member 208 as described inthe first embodiment, it is the first linear polarization. Thus, afterthe image light 3001 is transmitted through the reflective polarizationselection member 300, it is transmitted through the transmissionpolarization axis variable portion 400 as the first linear polarizationwithout its polarization axis being changed, is reflected by thereflective polarization selection member 301, and returns to the imagedisplay device 1000, whereby it is virtually not viewable to the viewer.

[0105] It should be noted that, as described in the first embodiment, itis preferable to switch, to the dark display, the display region of theimage display portion 1000 corresponding to the region that becomes themirror status, in order to further reduce leakage of light from theimage display portion 1000 side in the mirror status. When the entiredisplay region is switched to the mirror status, leakage of light canalso be eliminated by switching the lighting system of the image displayportion to a non-emitting state.

[0106] In this manner, in the display device of the second embodiment,because virtually all of the polarization components of the outsidelight 3002 are reflected at the time of the mirror status, an extremelybright reflection image is obtained and an easy-to-view mirror isobtained with little light leakage of the image light 3001. Also, in thecase of the image display status, similar to the first embodiment, thereis little glare of the outside light, and a bright image can bedisplayed.

[0107] It should be noted that, although a member whose reflectionpolarization axis is parallel to the polarization axis of the firstlinear polarization and whose transmission polarization axis is parallelto the polarization axis of the second linear polarization was used inthe second embodiment as the second reflective polarization selectionmember 301, as shown in FIGS. 5 and 6, the present invention is notlimited to this configuration. A member whose reflection polarizationaxis is parallel to the polarization axis of the second linearpolarization and whose transmission polarization axis is parallel to thepolarization axis of the first linear polarization can also be used. Inthis case, the invention can be configured so that the display device isswitched to an image transmittance state by switching the transmissionpolarization axis variable portion 400 to a state that transmits withoutchanging the incident polarization axis (a state in which the voltage ison) and switching the variable polarization selection member 600 to astate that absorbs the second linear polarization and transmits thefirst linear polarization (a state in which the voltage is off), and sothat the display device is switched to the mirror status by switchingthe transmission polarization axis variable portion 400 to a state thatchanges the first linear polarization to the second linear polarization(a state in which the voltage is off) and switching the variablepolarization selection member 600 to a state that transmits allpolarization components (a state in which the voltage is on).

[0108] It should be noted that, in the first and second embodiments,although a transmissive liquid crystal element including the lightingsystem was described in a case where a liquid crystal element was usedas the image display portion 1000, it is also possible to use areflective liquid crystal element.

[0109] Also, when P1 represents the degree of polarization of theabsorbing polarization selection member 208 configuring the imagedisplay member and P2 represents the degree of polarization of theabsorbing polarization selection member 500, it is preferable that therelationship of 0.966.P1.0.995≦P2 is satisfied or that the relationshipof 0.966≦P2≦0.995≦P1 is satisfied. The reason for this will be describedlater in Example 2.

[0110] Also, in the display device of the first and second embodiments,it is preferable to form an antireflection film on the surfaces of theabsorbing polarization selection members 500 and 208 and on theoutermost surface of the variable polarization selection member 600.

[0111] Also, in the invention, it is preferable to set the intervalbetween the reflective polarization selection member 300 and thereflective polarization selection member 301 to 0.11 mm or less. Thereason for this will be described later in Example 2.

[0112] Also, when the display device is switched to the mirror status,it is preferable to configure the invention so that at least an entireregion of 58.6 mm×39.1 mm substantially serves as the mirror. This is asize that is set considering that ¼ of an adult male face is reflected.This will also be described later in the examples.

[0113] Also, in the first and second embodiments, a film-like member canbe used as the reflective polarization selection members 300 and 301. Inthis case, it is preferable to either direct adhere the film-like member, via a transparent adhesive, to a transparent substrate that has highrigidity, is flat, transparent, and optically isotropic, or indirectlyadhere and fix the film-like member, via a flat film or the like, sothat there is no warping in the reflection surface.

[0114] Also, the display device of the first and second embodiments canbe a projection display device, in which projection light emitted from aprojection device is irradiated onto a transmissive screen via a mirrormember. In this case, the device may be configured so that thetransmissive screen is disposed with a mirror function portion. In thiscase, the device is configured so that the projection device is one thatemits, as the projection light, linear polarizations in which thepolarization state of each color light matches, and so that the linearlypolarized light is s-polarized light or p-polarized light with respectto the reflection surface of the mirror member.

[0115] Moreover, of the optical system and the mirror function portionconfiguring the transmissive screen, the device can be configured sothat the mirror function portion is a detachable structure that isremoved when the mirror function is unnecessary. Alternatively, thescreen may be configured so that the mirror function portion is disposedindependently, without including the image display portion, and themirror function screen may be configured to be fitted to an optionaldisplay device as needed.

[0116] In the first and second embodiments, members having aconfiguration in which a conductive metal linear pattern is disposed ata pitch of over a thousand angstroms (10⁻¹ m) can be used as thereflective polarization selection members 300 and 301. In this case, thelongitudinal direction of the metal linear pattern becomes thereflection polarization axis. Also, a reflective polarization selectionmember in which a conductive metal linear pattern is formed on atransparent substrate at a pitch of over a thousand angstroms (10⁻¹ m)and part of an adjacent linear pattern is electrically connected can beused together with the transparent electrode. Thus, the transparentelectrode 606 and the reflective polarization selection member 301, orthe reflective polarization selection member 301 and the transparentelectrode 403, or the transparent electrode 406 and the reflective.polarization selection member 300 can be configured.

[0117] In the first and second embodiments, the image display device1000 can be structured as follows. That is, the image display 1000 canhave a configuration disposed with: a liquid crystal element including apair of transparent substrates joined with a constant gap therebetween,a liquid crystal layer sandwiched between these transparent substrates,a pixel electrode group disposed in a matrix formed by a transparentelectrode on at least one of the pair of transparent substrates, theabsorbing polarization selection member 208 disposed at the viewer side,and an absorbing polarization selection member disposed on thetransparent substrate opposite from that of the viewer side; adisplay-use liquid crystal element drive portion that applies, to thepixel electrode group, a voltage corresponding to an image signal; and alighting system disposed at a rear surface of a display-use liquidcrystal element. In this case, the device can have a configurationdisposed with a switch portion that switches the lighting system on andoff in conjunction with the switching switch 813. The device can beconfigured so that the lighting system includes light sources thatsuccessively emit plural color lights and so that the liquid crystalelement conducts field-sequential color display in correspondence to thecolor lights from the lighting system.

[0118] Also, the device can be configured to use a reflective liquidcrystal element as the image display portion 1000. In this case, areflective liquid crystal element, in which a transparent substrate anda reflection substrate disposed with a reflective portion are adheredtogether via spacers such as beads, the surrounding area thereof issealed with a frame-like seal material, and liquid crystal is injectedbetween the two substrates and sealed, can be used. In this case, aphase-difference plate is laminated and disposed on the transparentsubstrate. It should be noted that the transparent substrate or thereflection substrate can be disposed with a color filter. It ispreferable for this color filter to be disposed with a function forraising brightness at the dark display. Specifically, it is morepreferable to use a delta arrangement color filter.

[0119] Also, the display device of the first and second embodiments canbe configured so that the sizes of the region that becomes the mirrorstatus and the image display region in the image display status aredifferent. Also, an image display portion having a configurationdisposed with a display-use liquid crystal element, which functions as atransmissive type at part of the display region and functions as areflective type at other regions, and a lighting system for illuminatingthe region functioning as the transmissive type can be used as the imagedisplay portion 1000.

[0120] Also, the display device of the first and second embodiments maybe configured so that the display region of the image display portion isplurally divided into regions, and so that switching between the mirrorstatus and the image display status is controlled per divided region. Inorder to realize this, the display device can be configured so that thelight-transmitting surfaces of the transmission polarization axisvariable portion 400 and the variable polarization selection member 600are divided into plural regions, so that selection between a state inwhich the polarization axis of the transmitted light is changed and astate in which the polarization axis of the transmitted light is notchanged is controlled per individual region, and so that selection ofpolarized light that is to be absorbed is controlled.

[0121] Examples of the invention will be described below.

EXAMPLE 1

[0122] A display device disposed with a function for switching to amirror status of Example 1 of the invention will be described usingFIGS. 7 and 8. The basic configuration of the display device of Example1 is the same as that of the display device shown in FIGS. 1 and 2 ofthe first embodiment.

[0123] Similar to the first embodiment, the display device of FIG. 7 ofExample 1 includes the image display portion 1000, the reflectivepolarization selection member 300, the transmission polarization axisvariable portion 400, and the absorbing polarization selection member500, which are successively superimposed. These are accommodated insidea case 1070 that includes an opening 1071. The opening 1071 serves as animage display portion capable of being switched to the mirror status.The action of each part is as was described in the first embodiment.

[0124] As shown in FIGS. 7 and 8, the image display portion 1000includes a liquid crystal display panel 200, which includes adisplay-use liquid crystal element and displays images by adjusting theamount of light transmitted therethrough, and a lighting system 100disposed at the rear surface of the liquid crystal display panel 200. Itis preferable to use, as theliquidcrystaldisplaypanel200,aliquidcrystaldisplaypanel that uses adisplay mode such as the TN (Twisted Nematic) mode, the STN(SuperTwisted Nematic) mode, and the ECB (Electrically ControlledBirefringence) mode. Because such a liquid crystal display panelconducts display by modulating the polarization state of light madeincident at the liquid crystal layer using a polarizing plate, a highcontrast ratio can be obtained with a relatively low drive voltage.Also, linearly polarized light is emitted as image light by thepolarizing plate that functions as the absorbing polarization selectionmember 208 disposed at the reflective polarization selection member 300side of the liquid crystal display panel 200.

[0125] As is commonly known, there are two formats for the liquidcrystal display panel 200—an active matrix drive liquid crystal displaypanel that uses a switching element such as a TFT (Thin FilmTransistor), and a multiplex drive liquid crystal display panel—andeither can be selected and used. Specifically, an active matrix driveliquid crystal display panel, such as a TN (Twisted Nematic) liquidcrystal display panel, an IPS (In Plane Switching) liquid crystaldisplay panel, and an MVA (Multi-domain Vertical Aligned) liquid crystaldisplay panel, or a multiplex drive liquid crystal display panel such asan STN (Super Twisted Nematic) liquid crystal display panel, can beused. Although a case will be described in Example 1 where a TN liquidcrystal display panel is used as the liquid crystal display panel 200,the present invention is not limited thereto.

[0126] Using FIG. 8, the detailed structure of each part of the displaydevice of Example 1 will be described.

[0127] A system that can evenly illuminate the image display portion ofthe liquid crystal display panel 200 is used for the lighting system100. As the lighting system, the edge light system (waveguide system),the directly-under system (reflector system), and the planar lightsource system (Ekisho disupurei gijutsu (“Liquid Crystal DisplayTechnology”), pp. 252-256, Sangyotosho Kabushikigaisha, published onNov. 8, 1996; Furukara ekisho hyoji gijutsu (“Full-color Liquid CrystalDisplay Technology”), pp. 201-202, Kabushikigaisha Torigeppusu,published on Feb. 26, 1990) are commonly known. As the lighting system100, an optimum system may be selected from these systems or othersystems to match purpose, object, or image size. Although descriptionwill be given here of a case where an edge light system is used as thelighting system 100, the invention is not limited thereto.

[0128] The lighting system 100 includes a waveguide 103 comprisingtransparent acrylic resin whose undersurface has been administered atreatment such as dot printing 105 by a white pigment, a linear lightsource 101 comprising, for example, a cold-cathode tube disposed at anend surface of the waveguide 103, a lamp cover 102, a reflective sheet104 disposed at the undersurface of the waveguide 103, diffusion sheets110 and 112 disposed at a front surface of the waveguide 103, and aprism sheet 111.

[0129] In this configuration, light emitted from the light source 101 isdirectly made incident on the waveguide 103 or made incident on thewaveguide 103 after being reflected by the lamp cover 102. Althoughlight 1101 made incident at the waveguide 103 is propagated within thewaveguide 103 while being reflected, the traveling direction of lightreaching the dot printing 105 by the white pigment administered to theundersurface of the waveguide 103 is changed and the light is emittedfrom the surface side of the waveguide 103. Light emitted from thewaveguide 103 is irradiated onto the liquid crystal display panel 200after its emission angle distribution and in-plane luminancedistribution are made even by the diffusion sheets 110 and 112 and theprism sheet 111.

[0130] As shown in FIG. 8, the liquid crystal display panel 200 includesa first transparent substrate 201 and a second transparent substrate 202comprising flat, transparent, and optically isotropic glass or plastic.A color filter (not shown), a transparent electrode 203 comprising ITO(Indium Tin Oxide), and an orientation film 204 comprising a polyimidepolymer are laminated on the transparent substrate 201. An orientationfilm 206, a transparent electrode 205 forming pixels, and a switchingelement (not shown) such as a thin-film transistor or an electrodeconnected thereto are formed on the second transparent substrate 202.The two transparent substrates 201 and 202 are joined with the surfaceshaving formed thereon the orientation films 204 and 206 facing, aconstant gap is disposed between the two transparent substrates 201 and202 via unillustrated spacers, the surrounding area thereof is sealedwith a frame-like seal material 210, and a space is formed inside. Aliquid crystal layer 207 is disposed by injecting nematic liquidcrystal, whose dielectric anisotropy is positive, into this space.

[0131] The orientation direction of the long axes of the liquid crystalmolecules of the liquid crystal layer 207 is defined by conducting anorientation treatment, such as rubbing, on the orientation films 204 and206 formed on the two transparent substrates 201 and 202. Here, they arecontinuously twisted 90° between the transparent substrates 201 and 202.A polarizing plate 209 and an absorbing polarization selection member(polarizing plate) 208 are respectively disposed on the rear surface ofthe transparent substrate 202 and the front surface of the transparentsubstrate 201 so that they transmit linear polarizations whosepolarization axes are mutually orthogonal. The orientation directions ofthe long axes of the liquid crystal molecules of the transparentsubstrate 202 and the transparent substrate 201 are configured so thatthey are both parallel to or orthogonal to the transmission polarizationaxes of the polarizing plate 209 and the absorbing polarizationselection member (polarizing plate) 208.

[0132] A plate in which a triacetylcellulose protection layer has beenadministered to both sides of a film to which a polarizing function hasbeen imparted by causing stretched polyvinyl alcohol to absorb iodinecan be used as the absorbing polarization selection member (polarizingplate) 208 and the polarizing plate 209. It should be noted that theabsorbing polarization selection member (polarizing plate) 208 and thepolarizing plate 209 are respectively adhered, so that they areoptically bonded by an acrylic adhesive, to the transparent substrate202 and the transparent substrate 201.

[0133] According to this configuration, of the illumination light madeincident from the back surface (lighting system 100 side) of the liquidcrystal display panel 200, the linear polarization transmitted throughthe polarizing plate 209 passes through the liquid crystal layer 207 andis made incident at the absorbing polarization selection member(polarizing plate) 208. At this time, the polarization state of thelight transmitted through the liquid crystal layer 207 can be changed bya voltage applied to the liquid crystal layer 207. Thus, by applying, tothe transparent electrodes 203 and 205, a voltage corresponding to imageinformation conveyed from an image information generating unit (notshown) and applying an electric field to the liquid crystal layer 207,the polarization state of the light passing through the liquid crystallayer 207 can be changed and the light amount transmitted through theabsorbing polarization selection member (polarizing plate) 208 can becontrolled. Thus, desired image light comprising linearly polarizedlight can be formed.

[0134] Next, the reflective polarization selection member 300 will bedescribed.

[0135] A member that includes the function of transmitting the firstlinear polarization component emitted from the image display portion1000 and mirror-reflecting the second linear polarization component,which has a polarization axis that is orthogonal to that of the firstlinear polarization component, is used for the reflective polarizationselection member 300. For example, the birefringence reflectivepolarization film disclosed in International Application InternationalPublication No. WO95/27919, in which different plural birefringencepolymer films are alternatingly laminated, or a member in which a ¼wavelength plate is disposed on the top and bottom of a cholestericliquid crystal layer, can be used as such a member. In the case of thebirefringence reflective polarization film, a film that transmits apredetermined linear polarization component and mirror-reflects a linearpolarization component whose polarization axis is orthogonal to that ofthe predetermined linear polarization component is commerciallyavailable under the brand name DBEF from 3M (U.S.), and this can be usedas the reflective polarization selection member 300. It should be notedthat, because the reflective polarization selection member 300 is animportant member functioning as a mirror surface when the presentdisplay device is switched to the mirror status, a member to which atreatment that can blur the reflection image, such as matting, has notbeen administered is used.

[0136] In a case where the reflective polarization selection member 300is configured by a member in which a ¼ wavelength plate is disposed onthe top and bottom of a cholesteric liquid crystal layer, a liquidcrystal cell in which low-molecular weight cholesteric liquid crystal isdisposed between two oriented transparent substrates, or a layer inwhich polymer cholesteric liquid crystal is formed on a flat, opticallyisotropic transparent substrate such as glass or transparent resin, canbe used as the cholesteric liquid crystal layer. The cholesteric liquidcrystal layer exhibits unique optical characteristics based on itshelical molecular arrangement, and exhibits selective reflection inwhich circularly polarized light of one rotational direction madeincident in parallel on the helical axis is reflected and circularlypolarized light of the other rotational direction is transmitted, incorrespondence to the rotational direction of the cholesteric spiral.The wavelength region of the selective reflection is determined by thepitch of the molecular arrangement, and it is necessary to laminate anduse plural cholesteric liquid crystal layers of different pitches inorder for the selective reflection to occur in the entire visiblewavelength region. In this case, in order to obtain selective reflectionin the entire visible wavelength region, the cholesteric liquid crystallayer in which pitch is continuously changed and that is described inAsia Display 95 Digest, p. 735, The Institute of Television Engineers ofJapan (ITE) & The Society for Information Display (SID), may be used inplace of laminating plural cholesteric liquid crystal layers ofdifferent pitches.

[0137] In the case where the member in which a ¼ wavelength plate isdisposed on the top and bottom of a cholesteric liquid crystal layer isused as the reflective polarization selection member 300, the lag axisof the ¼ wavelength plate disposed on the underside of the cholestericliquid crystal layer, i.e., on the image display portion 1000 side, isset in the following direction. That is, the lag axis is disposed sothat the first linear polarization emitted from the image displayportion 1000 and made incident at the reflective polarization selectionmember 300 is converted to a circular polarization transmitted throughthe cholesteric liquid crystal layer. Similarly, the lag axis of the ¼wavelength plate disposed on the top side of the cholesteric liquidcrystal layer, i.e., on the transmission polarization axis variableportion 400 side, is disposed so that a circular polarizationtransmitted through the cholesteric liquid crystal layer is converted tothe first linear polarization.

[0138] When the second linear polarization is made incident at thereflective polarization selection member of the configuration in which a¼ wavelength plate is disposed on the top and bottom of a cholestericliquid crystal layer, the second linear polarization is selectivelyreflected by the cholesteric liquid crystal layer because it isconverted, by the action of the ¼ wavelength plates, to a circularpolarization that is the reverse of the circular polarizationtransmitted through the cholesteric liquid crystal layer. When thecircular polarization reflected by the cholesteric liquid crystal layeris again transmitted through the ¼ wavelength plates, it is converted bythe action thereof to the second linear polarization.

[0139] It should be noted that it is preferable to use, as the ¼wavelength plates used in the reflective polarization selection member300 of this configuration, plates that function as ¼ wavelength platesin the entire visible wavelength region. A stretched polymer film thathas high transmittance in the visible wavelength region, such aspolyvinyl alcohol, polycarbonate, polysulfone, polystyrene, andpolyarylate, can be used as the ¼ wavelength plate. In addition, mica,crystal, or a liquid crystal layer in which the molecular axes thereofhave been oriented in one direction can also be used.

[0140] Also, although it is difficult to configure a phase-differenceplate functioning as a ¼ wavelength plate with respect to the entirevisible wavelength region with one type of phase-difference plate due towavelength dependency (below, wavelength dispersion) of the refractiveindex of materials commonly configuring ¼ wavelength plates, a plateconfigured to function as a ¼ wavelength plate in a wide wavelengthregion by adhering together at least two types of phase-differenceplates whose wavelength dispersion is different so that the optical axesthereof are orthogonal may be used.

[0141] Attention should be given to the following points when afilm-like material, such as the birefringence reflective polarizationfilm or a laminate member of the film-like cholesteric liquid crystallayer and the ¼ wavelength plates, is used as the reflectivepolarization selection member 300.

[0142] That is, because the flatness of a film-like reflectivepolarization selection member, as it is, is low, there is a lot ofwarping and it is difficult to realize a practically satisfactory mirrorsimply by disposing it on the front surface of the image display portion1000. Thus, when a film-like member is used as the reflectivepolarization selection member 300, it is preferable to adhere and fixit, via a transparent adhesive, to a transparent substrate that isoptically isotropic, transparent, flat and has high rigidity, such as aglass plate or a plastic plate, so that there is no warping.

[0143] Alternatively, in order to fix the reflective polarizationselection member 300 in a flat state, it can be fixed to the transparentsubstrate of the transmission polarization axis variable portion 400described later or the liquid crystal display panel 200 in place ofadhering and fixing it to a new transparent substrate. In any event,when a film-like member is used as the reflective polarization selectionmember 300, it is preferable to adhere and fix it to another flat memberin order to realize a mirror with no warping.

[0144] Next, the transmission polarization axis variable portion 400will be described.

[0145] The transmission polarization axis variable portion 400 has aconfiguration in which it is possible to select, when incident linearlypolarized light is transmitted therethrough, between one of a state thatchanges the polarization state of the incident linearly polarized light,so that it is changed to linearly polarized light whose polarizationaxis is orthogonal to that of the incident linearly polarized light, anda state that does not change the polarization axis of the incidentlinearly polarized light. For example, a liquid crystal element such asthe one shown in FIG. 8 can be used.

[0146] The transmission polarization axis variable portion 400 includesa first transparent substrate 401, in which a transparent electrode 403comprising ITO and an orientation film 404 comprising a polyimidepolymer are laminated and formed on the entire surface thereof, a secondtransparent substrate 402, in which a transparent electrode 406 and anorientation film 405 are similarly laminated and formed on the entiresurface thereof, and a liquid crystal layer 407. It should be noted thatthe transparent electrodes 403 and 406 respectively formed on the twotransparent substrates 401 and 402 are connected to a power source (seeFIG. 1; not shown in FIG. 8) via unillustrated wiring and the switchingswitch 813. Thus, the transmission polarization axis variable portion400 is configured to be selectable between one of a state in whichvoltage is not applied and a state in which voltage is applied to thetransparent electrodes 403 and 406. In other words, the transmissionpolarization axis variable portion 400 is configured to be selectablebetween one of a state in which that there is no difference in electricpotential between the transparent electrodes 403 and 406 and an electricfield is not applied to the liquid crystal layer 407 and a state inwhich voltage is applied to the transparent electrodes 403 and 406 andan electric field is applied to the liquid crystal layer 407.

[0147] The liquid crystal layer 407 of the transmission polarizationaxis variable portion 400 is configured by disposing the two transparentsubstrates 401 and 402 so that the surfaces on which the orientationfilms are formed face each other, disposing a constant gap between thetwo transparent substrates 401 and 402 by sandwiching unillustratedspacers therebetween, sealing, in a frame shape, the area surroundingthe gap with a seal material 410, forming a space, and injecting intothis space nematic liquid crystal whose dielectric anisotropy ispositive.

[0148] Here, a case where a so-called TN liquid crystal element, whichis configured so that orientation processing such as rubbing isconducted for each of the orientation films 404 and 405 formed on thetwo transparent substrates 401 and 402 and the liquid crystal moleculelong axes of the liquid crystal layer 407 are continuously twisted 90°between the two transparent substrates 401 and 402, will be described asthe transmission polarization axis variable portion 400.

[0149] In this case, the orientation direction of the liquid crystalmolecule long axes of the transparent substrate 402 side is configuredso as to be parallel or orthogonal to the linear polarizationtransmission polarization axis o f the absorbing polarization selectionmember (polarizing plate) 208 of the liquid crystal display panel 200,and the liquid crystal layer 407 is configured to satisfy waveguideconditions in the visible wavelength region. The waveguide conditionsare described in, for example, the thesis by C. H. Gooch and H. A. Tarryon pp. 1575-1584 of J. Phys. D: Appl. Phys., Vol. 8 (1975).

[0150] Here, when An represents the birefringence of the liquid crystaland d represents the thickness of the liquid crystal layer, d×Δn=0.4452(633 nm wavelength).

[0151] According to the above-described configuration, in an OFF statein which there is no difference in electric potential between thetransparent electrodes 403 and 406 respectively formed on the twotransparent substrates 401 and 402 and an electric field is not appliedto the liquid crystal layer 407, the transmission polarization axisvariable portion 400 of the present example changes the first linearpolarization, which is emitted from the image display portion 1000 andis transmitted through the reflective polarization selection member 300,to the second linearly polarized light whose polarization axis isorthogonal to that of the first linear polarization. Additionally, in anON state in which voltage is applied to the transparent electrodes 403and 406 respectively formed on the two transparent substrates 401 and402 and an electric field is applied to the liquid crystal layer 407,the transmission polarization axis variable portion 400 transmits thefirst linearly polarized light, which is emitted from the image displayportion 1000 and transmitted through the reflective polarizationselection member 300, without changing its polarization axis. At thistime, the voltage applied to the transparent electrodes 403 and 406functions sufficiently as long as it is ±5V, 60 Hz.

[0152] It should be noted that, although a case was described in Example1 in which the TN liquid crystal element was used as the transmissionpolarization axis variable portion 400, the present invention is notlimited thereto. That is, it suffices as long as the transmissionpolarization axis variable portion 400 is a portion that is selectable,when incident linearly polarized light is transmitted therethrough,between a state that changes the polarization axis of the incidentlinearly polarized light, so that it is changed to linearly polarizedlight whose polarization axis is orthogonal to that of the incidentlinearly polarized light, and a state that does not change thepolarization axis of the incident linearly polarized light. An ECB(Electrically Controlled Birefringence) liquid crystal element, aferroelectric liquid crystal element, and an antiferroelectric liquidcrystal element or the like can be used in addition to the TN liquidcrystal element.

[0153] Next, the absorbing polarization selection member 500 will bedescribed.

[0154] The absorbing polarization selection member 500 is a memberincluding the function of absorbing the first linear polarizationcomponent of the incident light and transmitting the second linearpolarization component, whose polarization axis is orthogonal to that ofthe first linear polarization component, or transmitting the firstlinear polarization component and absorbing the second linearpolarization component, and a so-called polarizing plate can be used. Inother words, a polarizing plate, in which a triacetylcelluloseprotection layer has been administered to both sides of a film to whicha polarizing function has been imparted by causing stretched polyvinylalcohol to absorb iodine, can be used as the absorbing polarizationselection member 500.

[0155] It should be noted that it is preferable to administer, to thesurface of the absorbing polarization selection member 500, a treatmentfor suppressing regular reflectance in order to suppress deteriorationof image quality resulting from glare. However, that which is importanthere is that, in order for the display device of the invention to alsofunction as a mirror, methods that reduce regular reflection component,such as forming minute recesses and projections on the surface orforming a transparent resin layer including transparent particles on thesurface, are not preferable as the treatment for preventing regularreflectance of the absorbing polarization selection member 500. Thereason for this is because, when such a treatment is administered,although image display performance is improved due to a reduction ofglare, the problem arises that the image reflected in the mirror becomesblurry and the performance of the mirror deteriorates.

[0156] Therefore, as the treatment for preventing regular reflectance ofthe absorbing polarization selection member 500, it is preferable toform an antireflection film on the surface thereof. Well knowntechnology can be used for the antireflection film. That is, it sufficesas long as it is a method in which multilayers of several types of metaloxides having different optically designed refractive indexes are coatedby vapor deposition or a method in which a low refractive index materialsuch as a fluorine compound is coated.

[0157] Next, the direction of the axis of each member of the displaydevice of the present example will be described using FIG. 9.

[0158] Here, a case is described in which the absorbing polarizationselection member 500 absorbs the first linear polarization component ofthe incident light and transmits the second linear polarizationcomponent whose polarization axis is orthogonal to that of the firstlinear polarization component. It should be noted that the angle of eachaxis uses, as a reference, a position at 3 o'clock in a horizontaldirection of the image display surface, and is represented by an anglecounterclockwise from here. As shown in FIG. 9, when a TN liquid crystaldisplay panel is used as the liquid crystal display panel 200configuring the image display portion 1000, the transmissionpolarization axis of the linear polarization of the polarizing plate isordinarily 135° (or 45°; in the present example, 135°) in order toobtain horizontal direction symmetry of viewing angle characteristics.Therefore, the transmission polarization axis of the linear polarizationof the reflective polarization selection member 300 is similarly 135°,the orientation directions of the liquid crystal molecule long axes ofthe transparent substrate 401 and the transparent substrate 402 of thetransmission polarization axis variable portion 400 are 135° and 45°,respectively, and the transmission polarization axis of the linearpolarization of the absorbing polarization selection member 500 is 45°.

[0159] Next, the operation of the display device of Example 1 will bedescribed using FIGS. 10 and 11.

[0160] A case where the display device of Example 1 is in the imagedisplay status will be described using FIG. 10. When the display deviceis in the image display status, the switching switch 813 is switched offso that the transmission polarization axis variable portion 400 is in astate in which voltage is not applied to the liquid crystal layer 407configuring the transmission polarization axis variable portion 400,i.e., is in an OFF state. A linear polarization that is emitted from thelighting system 100 of the image display portion 1000 and transmittedthrough the absorbing polarization selection member (polarizing plate)208 of the liquid crystal display panel 200 is emitted as the imagelight 3001 from the image display portion 1000. The image light 3001comprising the first linear polarization is transmitted through thereflective polarization selection member 300 and made incident at thetransmission polarization axis variable portion 400. The image light3001 passing through the transmission polarization axis variable portion400 is changed from the first linear polarization to the second linearpolarization. The image light 3001 of the second linear polarizationtransmitted through the transmission polarization axis variable portion400 is made incident at the absorbing polarization selection member 500.Because the absorbing polarization selection member 500 absorbs thefirst linear polarization component and transmits the second linearpolarization component, the image light 3001 of the second linearpolarization is transmitted through the absorbing polarization selectionmember 500 and is viewable to the viewer.

[0161] Although the outside light 3002 made incident at the displaydevice from the viewer side (the left side in the drawing) isnon-polarized light, when it is transmitted through the absorbingpolarization selection member 500, the first linear polarizationcomponent is absorbed and only the second linear polarization componentis transmitted. When the outside light 3002 transmitted through theabsorbing polarization selection member 500 is transmitted through thetransmission polarization axis variable portion 400, it is changed fromthe second linear polarization to the first linear polarization,transmitted through the reflective polarization selection member 300 andproceeds toward the image display portion 1000. As described in thefirst embodiment, this light virtually does not return to the viewerside.

[0162] Therefore, in the image display status, a bright image can beobtained because the image light 3001 emitted from the image displayportion 1000 proceeds toward the viewer with virtually no loss.Moreover, because the outside light 3002 is not reflected by thereflective polarization selection member 300 functioning as a mirror inthe case of the mirror status, there is virtually no deterioration ofimage quality resulting from the outside light, such as a drop incontrast and glare.

[0163]FIG. 11 shows a case where the display device is in the mirrorstatus. When the display device is in the mirror status, the switchingswitch 813 is switched on so that the transmission polarization axisvariable portion 400 is in an ON state in which an electric field isapplied to the liquid crystal layer 407 configuring the transmissionpolarization axis variable portion 400. In this case, although theoutside light 3002 proceeding from the viewer side to the display deviceis non-polarized light, when it is transmitted through the absorbingpolarization selection member 500, the first linear polarizationcomponent is absorbed and only the second linear polarization componentis transmitted and made incident at the transmission polarization axisvariable portion 400. The outside light 3002 made incident at thetransmission polarization axis variable portion 400 at this time istransmitted through the transmission polarization axis variable portion400 as the second linearly polarized light, without its polarizationaxis being changed, and reaches the reflective polarization selectionmember 300. Because the reflective polarization selection member 300transmits the first linear polarization component and mirror-reflectsthe second linear polarization component, the outside light 3002 isreflected by the reflective polarization selection member 300. Becausethe outside light 3002 reflected by the reflective polarizationselection member 300 is transmitted through the transmissionpolarization axis variable portion 400 as the second linear polarizationwithout its polarization axis being changed, and is also transmittedthrough the polarization selection member 500 and proceeds toward theviewer, the mirror status is realized.

[0164] At this time, because the image display portion 1000 of thepresent example is disposed with the absorbing polarization selectionmember (polarizing plate) 208, the image light of the dark displayregion is absorbed by the absorbing polarization selection member(polarizing plate) 208 and does not reach the reflective polarizationselection member 300. Thus, leakage of light from the dark displayregion can be largely reduced, regardless of the reflective capabilityof the reflective polarization selection member 300.

[0165] Also, of the image light emitted from the image display portion1000, the image light 3001 emitted from the bright display region istransmitted through the reflective polarization selection member 300 andmade incident at the transmission polarization axis variable portion400. In a case where the present display device is in the mirror status,because the transmission polarization axis variable portion 400 is in anON state and the image light 3001 transmitted through the transmissionpolarization axis variable portion 400 at this time is transmittedtherethrough as the first linearly polarized light without itspolarization axis being changed, it is absorbed by the absorbingpolarization selection member 500 and is virtually not viewable to theviewer.

[0166] In other words, in the case of the mirror status, because thelight from the image display member does not reach the viewer and halfthe light of the non-polarized light of the outside light 3002 madeincident at the display device from the surrounding area is ideallyreflected by the reflective polarization selection member 300 andproceeds toward the viewer side, the light functions as a bright mirror.

[0167] Also, the display device of the present example has aconfiguration in which, at the time of the mirror status, thetransmission polarization axis variable portion 400 is switched on andthe liquid crystal molecules 407 a are made to stand. Usually, with anematic liquid crystal, there is less offset of the polarization axis oflight emitted in a diagonal direction when the voltage is on and theliquid crystal molecules are made to stand than when the voltage is offand the liquid crystal molecules are twisted. For this reason, with thedisplay device of the present embodiment, the effect can also beobtained that there is little leakage of light in a diagonal directionof the image light (bright display light) 3001 in the mirror status incomparison to the display device of the configuration in which thevoltage is off in the mirror status described in the conventional art.

[0168] It should be noted that the characteristics of the polarizingplates functioning as the absorbing polarization selection member 208and the absorbing polarization selection member 500 are directly relatedto the image quality of the image display status and the ease with whichthe mirror of the mirror status can be viewed. Specifically, it ispreferable for the transmittance of the polarizing plates to be high inorder to contribute to the brightness of an image in the image displaystatus and the brightness of the reflection image in the mirror status.Also, the degree of polarization of the polarizing plates is directlyrelated to the amount of unnecessary reflection of outside light andthe. contrast ratio in the image display status. Because the higher thedegree of polarization of the polarizing plates is, the higher thecontrast of the image display becomes and the smaller unnecessaryreflection of outside light becomes, it is preferable for the degree ofpolarization of the polarizing plates to be high. Even in the mirrorstatus, because the higher the degree of polarization is, the smallerleakage of light from the image display member becomes, the contrastratio of the reflection image is improved, and an easy-to-view mirrorstatus is realized, it is preferable for the degree of polarization ofthe polarizing plates to be even higher.

[0169] Therefore, it is preferable to use polarizing plates that havehigh transmittance and a high degree of polarization for the polarizingplates used as the absorbing polarization selection member 208 and theabsorbing polarization selection member 500. However, there usuallyexists a trade-off relationship, such as exemplified in FIG. 12, betweenthe degree of polarization and the transmittance of the polarizingplates (Nitto giho, Vol. 38, No. 1, May 2000, pp. 11-14). FIG. 12 is agraph showing a common relationship between the degree of polarizationand the transmittance of an iodine polarizing plate. The horizontal axisrepresents transmittance of the polarizing plate, and the vertical axisrepresents the degree of polarization. For this reason, the selection ofcharacteristics of the polarizing plates used as the absorbingpolarization selection member 208 and the absorbing polarizationselection member 500 becomes extremely important for balancing the imagequality of the image display status and mirror performance in the mirrorstatus.

[0170]FIGS. 3 and 4 are graphs showing leakage of light from the imagedisplay portion 1000 in the mirror status. FIG. 3 shows, in luminancevalues, the magnitude of leakage of light at the bright display region,and FIG. 4 shows, in luminance values, the magnitude of leakage of lightat the dark display region. These graphs are data of conditions in whichbright display at a luminance of 450 cd/m² was conducted in a case wherethe display device was in the image display status. The horizontal axesrepresent positions on the display device display portion, and thevertical axes represent luminance values in a front direction. In thedrawings, the A-type polarizing plate, the B-type polarizing plate, andthe C-type polarizing plate represent types of polarizing plates used asthe absorbing polarization selection member 208. For comparison, lightleakage in a display device in which the absorbing polarizationselection member 208 was eliminated and in which other configurationswere the same as those of the image device of the present Example 1 isalso included. With respect to the A-type polarizing plate of FIGS. 3and 4, transmittance was 41.5% and the degree of polarization was99.97%. With respect to the B-type polarizing plate, transmittance was43.6% and the degree of polarization was 99.5%. With respect to theC-type polarizing plate, transmittance was 45.5% and the degree ofpolarization was 96.60%. It should be noted that the data of FIGS. 3 and4 used the A-type polarizing plate as the absorbing polarizationselection member 500.

[0171] As shown in FIGS. 3 and 4, it will be understood that leakage oflight was remarkably reduced by disposing the absorbing polarizationselection member 208, regardless of which of the A-type, B-type, orC-type polarizing plates was used, in comparison to the case in whichthere was no absorbing polarization selection member 208, and a mirrorthat reflected a reflection image having a high contrast ratio could berealized. It will be understood that, particularly in the cases of theA-type and B-type polarizing plates, in which the degree of polarizationwas 99.5% or higher, leakage of light at the dark display portion wasremarkably reduced, as shown in FIG. 4, and a high-definition mirrorstatus that reflected a reflection image with an even higher contrastratio could be realized.

[0172] Therefore, it is preferable for the degree of polarization of thepolarizing plate used as the absorbing polarization selection member 208to be at least 96.60% or higher, and even more preferable for the degreeof polarization to be 99.5% or higher in order to realize an evenhigher-definition mirror status.

[0173]FIG. 13 is a graph showing the relationship between the degree ofpolarization of the polarizing plate used as the absorbing polarizationselection member 500 and reflectance of the mirror in the mirror statusand reflectance (unnecessary reflectance) of outside light in the imagedisplay status. The horizontal axis represents the degree ofpolarization of the polarizing plate used as the absorbing polarizationselection member 500, and the vertical axis represents the reflectance.As shown in FIG. 13, by lowering the degree of polarization of thepolarizing plate used as the absorbing polarization selection member 500from 99.97% to 96.60% and making the polarizing plate more highlytransmissive, the reflectance in the mirror status was improved by about10% and a brighter mirror could be realized. At this time, the increasein unnecessary reflectance in the image display status was small.

[0174]FIG. 14 is a graph showing one example of the relationship betweenthe degree of polarization of the polarizing plate used as the absorbingpolarization selection member 208 and luminance values of the brightdisplay in the image display status. The horizontal axis represents thedegree of polarization of the polarizing plate, and the vertical axisrepresents relative luminance. It should be noted that the data of FIG.14 is data in the case where the A-type polarizing plate was used as theabsorbing polarization selection member 500. As shown in FIG. 14, bylowering the degree of polarization of the polarizing plate used as theabsorbing polarization selection member 208 from 99.97% to 96.60% andmaking the polarizing plate more highly transmissive, luminance rose byabout 9.5%, and a brighter image was obtained. This relationship was thesame as the case where the characteristics of the polarizing plate ofthe absorbing polarization selection member 208 were fixed and thedegree of polarization of the polarizing plate of the absorbingpolarization selection member 500 was changed.

[0175] Also, by using a polarizing plate having a degree of polarizationof 99.5% or higher for one of the absorbing polarization selectionmember 208 and the absorbing polarization selection member 500, asufficient contrast ratio could be obtained even if the degree ofpolarization of the other polarizing plate was 96.6% or less. Therefore,in order to improve luminance while maintaining a sufficient contrastratio in the image display status, it is effective to use a polarizingplate with a high degree of polarization for one of the absorbingpolarization selection member 208 and the absorbing polarizationselection member 500 and to use a polarizing plate having a low degreeof polarization for the other.

[0176] From the above, when P1 represents the degree of polarization ofthe polarizing plate of the absorbing polarization selection member 208and P2 represents the degree of polarization of the polarizing plate ofthe absorbing polarization selection member 500, it is preferable thatthe following conditions are satisfied in order to balance, at a highlevel, the contrast ratio and brightness of the display image in theimage display status and brightness and contrast ratio of the reflectionimage in the mirror status.

[0177] Condition 1: 0.966≦P1≦995≦P2

[0178] Condition 2: 0.966≦P2≦0.995≦P1 is satisfied, and the imagedisplay member is invariably switched to the dark display in the mirrorstatus.

[0179] The reason that the image display member is invariably switchedto the dark display in the mirror status in condition 2 is because, whenthe degree of polarization of the polarizing plate of the absorbingpolarization selection member 500 is low, leakage of light from thebright display region becomes large and the contrast ratio of thereflection image drops remarkably. Thus, by switching the image displaymember to the dark display, leakage of light is prevented and a drop inthe contrast ratio is prevented.

[0180] In the display device of Example 1, a switching portion thatswitches the lighting system 100 on and off in conjunction with theswitching of the switching switch 813 of the transmission polarizationaxis variable portion 400 may be disposed, so that the lighting systemis switched off when the entire screen is in the mirror status. In thiscase, because light is not outputted from the image display portion1000, there are also the effects that an easy-to-view mirror, in which areflection image having a high contrast ratio is obtained, can berealized with no leakage of light, and power consumption of the displaydevice can be reduced only by the amount turned off.

[0181] Also, when only part of the screen is switched to the mirrorstatus and an image is displayed on the remaining portion, a mirror thatrealizes a reflection image having a high contrast ratio can be realizedand a bright image display region can be realized on the same screen byswitching the region of the image display portion 1000 corresponding tothe region of the mirror status to the dark display without switchingthe lighting system off, and a bright image display region can berealized on the same screen.

[0182] As described above, according to the display device of thepresent invention, the reflective polarization selection member 300 canbe switched between an effectively transparent state and a statefunctioning as a mirror, due to control of the polarization state by thetransmission polarization axis variable portion 400. Therefore, a brightimage is obtained by switching the reflective polarization selectionmember 300 to the effectively transparent state in the image displaystatus. Also, because outside light is virtually not reflected in thedisplay device even in an environment in which the surrounding area isbright, deterioration of image quality, such as glare when a half mirroris used or a drop in contrast ratio accompanying glare, does not arise.In other words, switching between the image display status and themirror status can be realized without deteriorating their mutualperformance.

[0183] Also, because the image display portion 1000 of the presentexample is disposed with the absorbing polarization selection member(polarizing plate) 208, the image light of the dark display region isabsorbed by the absorbing polarization selection member (polarizingplate) 208 and does not reach the reflective polarization selectionmember 300. Thus, leakage of light from the dark display region in themirror status can be largely reduced, regardless of the reflectivecapability of the reflective polarization selection member 300.

[0184] It should be noted that, although a case was described in theabove-described example in which the absorbing polarization selectionmember 500 transmits the second linear polarization component andabsorbs the first linear polarization component, whose polarization axisis orthogonal to that of the second linear polarization component, amember that transmits the first linear polarization component andabsorbs the second linear polarization component may be used as theabsorbing polarization selection member 500. In this case, thetransmission polarization axis variable portion 400 is switched to themirror status in a state in which voltage is not applied to the liquidcrystal layer 407, i.e., in an OFF state, and the transmissionpolarization axis variable portion 400 is switched to the image displaystatus in a statue in which voltage is applied to the liquid crystallayer 407, i.e., in an ON state. That is, it can be switched to themirror status when the power of the entire display device is off. Thisbecomes very advantageous when the display device is used in instrumentssuch as handheld PCs and mobile telephones, with respect to which powerconsumption is desired to be made as small as possible, because themirror function can be realized in a state in which there is no powerconsumption.

[0185] It should be noted that, in order to reduce reflectance of lightat the interfaces of the structural members in the display device ofExample 1, it is possible to optically bond each member with atransparent adhesive that combines their refractive indexes.

EXAMPLE 2

[0186] A display device disposed with a function for switching to amirror status of Example 2 of the invention will be described usingFIGS. 15 and 16. The basic configuration of the display device ofExample 2 is the same as that of the display device shown in FIGS. 1 and2 of the second embodiment. That is, the display device of Example 2 isa device in which the absorbing polarization selection member 500 of thedisplay device described in Example 1 is replaced with a combination ofa reflective polarization selection member 301 and a variablepolarization selection member 600. Therefore, the same referencenumerals will be given to portions that are the same as those in Example1, and detailed description of those portions will be omitted.

[0187] As shown in FIGS. 15 and 16, the configuration of the displaydevice is one in which the reflective polarization selection member 301,which reflects the first linearly polarized light component andtransmits the second linearly polarized light component, and thevariable polarization selection member 600, which is selectable betweenone of a state that absorbs the first linear polarization component ofthe incident light and transmits the second linear polarizationcomponent and a state that transmits all polarization components, aresuccessively disposed from the transmission polarization axis variableportion 400 side in place of the absorbing polarization selection member500 of the display device of Example 1.

[0188] It should be noted that the viewer views the display device fromthe variable polarization selection member 600 side (left side in thedrawings).

[0189] As the image display portion 1000, an image display portionconfigured by the liquid crystal display panel 200, which displays animage by adjusting the amount of light transmitted therethrough, and thelighting system 100 disposed at the rear surface of the liquid crystaldisplay panel 200 can used.

[0190] In Example 2, although a case will be described with reference toFIG. 16 in which, similar to (Example 1), an edge light system is usedas the lighting system 100 and a TN liquid crystal display panel is usedas the display panel 200, the present invention is not limited thereto.

[0191] The reflective polarization selection member 300 and thereflective polarization selection member 301 transmit a predeterminedlinear polarization component and mirror-reflect a linear polarizationcomponent having a polarization axis orthogonal to that of thepredetermined linear polarization component. The birefringencereflective polarization film or the member in which a ¼ wavelength plateis laminated on the top and bottom of a chlorestic liquid crystal layerdescribed in (Example 1) can be used as these members.

[0192] When the birefringence reflective polarization film or thefilm-like member that is the laminate member of the film-like chloresticliquid crystal layer and the ¼ wavelength plates is used as thereflective polarization selection member 300 and the reflectivepolarization selection member 301, the following is done. That is,because the flatness of the film-like reflective polarization selectionmember is low as it is, it is preferable to adhere and fix it, via atransparent adhesive, to a transparent substrate that is opticallyisotropic, transparent, flat and has high rigidity, such as a glassplate or a plastic plate, so that there is no warping. The film-likereflective polarization selection member 300 and the reflectivepolarization selection member 301 may also be adhered and fixed to asubstrate of another member adjacent to the transparent substrate of theliquid crystal display panel 200.

[0193] The transmission polarization axis variable portion 400 is aportion that is selectable between one of a state that changes thepolarization axis of incident linearly polarized light when incidentlinearly polarized light is transmitted therethrough, to thereby changethe incident linearly polarized light to linearly polarized light whosepolarization axis is orthogonal to that of the incident linearlypolarized light, and a state that does not change the polarization axis,and the liquid crystal element described in (Example 1) can be used.

[0194] In the present example, the transmission polarization axisvariable portion 400 is disposed between the reflective polarizationselection member 300 and the reflective polarization selection member301. The reflective polarization selection member 300 and the reflectivepolarization selection member 301 are members that function asreflection surfaces when the present display device is switched to themirror status. For this reason, it is preferable to make the intervalbetween the two as small as possible because parallax arises in therespective image reflected by the reflective polarization selectionmember 300 and the reflective polarization selection member 301 when theinterval between the reflective polarization selection member 300 andthe reflective polarization selection member 301 increases. In otherwords, it is preferable to thin as much as possible the thickness of thetransmission polarization axis variable portion 400 disposed between thereflective polarization selection member 300 and the reflectivepolarization selection member 301.

[0195] The display device of Example 2 is primarily used for a person toview his/her reflected face in the mirror status. Given that the averageheight of an entire face of an adult male is 234.6 mm (Ningen kogakukijun suchi sushiki binran (“Handbook of Ergonomic Standard NumericalValues and Mathematical Formulas”), 1992, Gihodo Shuppan), when it ispresumed that the vertical distance from the eyes to the end of the faceis half of that, or 117.3 mm, that the distance between display devicein the mirror status and the eyes is 300 mm, and consideration is givento the fact that “the definition of resolution of average visual acuity1.0 is a minimum of 1 minute at a viewing angle” (definition ofeyesight; 1909 International Congress of Ophthalmology), it ispreferable for the interval between the reflective polarizationselection member 300 and the reflective polarization selection member301 to be 0.11 mm or less from geometrical calculation in order forparallax to not be felt.

[0196] In other words, at present, when a 0.7 mm-thick glass substrate,which is commonly used in liquid crystal elements, is used for thetransparent substrates 401 and 402 of the transmission polarization axisvariable portion 400 , parallax is generated in the reflected image whenthe present display device is in the mirror status. Therefore, in orderto practically realize a mirror without parallax, it is preferable touse a transparent substrate of 0.05 mm or less as the transparentsubstrates 401 and 402. Glass or polymer film can be used for thetransparent substrates 401 and 402. As the polymer film, particularlyone without optical anisotropy, triacetylcellulose, or unstretchedpolycarbonate formed in a film by casting (solvent casting), can beused.

[0197] Alternatively, by disposing the reflective polarization selectionmember 300 and the reflective polarization selection member 301 furthertoward the liquid crystal layer 407 side than the transparent substrates401 and 402, so that the liquid crystal layer 407 is sandwichedtherebetween, a mirror status without parallax can be realized becausethe interval between the reflective polarization selection member 300and the reflective polarization selection member 301 becomes about thethickness of the liquid crystal layer.

[0198] It should be noted that, because some parallax is allowabledepending on the purpose, the present invention is not one that excludescases where the interval between the reflective polarization selectionmember 300 and the reflective polarization selection member 301 is notthe above-described value.

[0199] The variable polarization selection member 600 is a member thatis selectable between one of a state that absorbs the first linearpolarization component of the incident light and transmits the secondlinear polarization component, whose polarization axis is orthogonal tothat of the first linear polarization component, and a state thattransmits all polarization components. A guest host liquid crystalelement can be used as such a member. Here, a variable polarizationselection member 600 that uses a guest host liquid crystal element willbe described with reference to FIGS. 17 and 18.

[0200] The variable polarization selection member 600 that uses a guesthost liquid crystal element includes a first transparent substrate 601,on the entire surface of which are laminated and formed a transparentelectrode 603 comprising ITO and an orientation film 604 comprising apolyimide polymer, a second transparent substrate 602, on the entiresurface of which are laminated and formed a transparent electrode 606and an orientation film 605, and a guest host liquid crystal layer 607sandwiched therebetween.

[0201] The transparent electrodes 603 and 606 respectively formed on thetwo transparent substrates 601 and 602 are connected to a power sourcevia wiring and a switching switch 600 a, and are selectable between oneof a state in which voltage is not applied to the transparent electrodes603 and 606 and a state in which voltage is applied. In other words,they are formed so as to be selectable between one of a state in whichthere is no difference in potential between the transparent electrodes603 and 606 and an electric field is not applied to the liquid crystallayer 607 and a state in which voltage is applied to the transparentelectrodes 603 and 606 and an electric field is applied to the liquidcrystal layer 607.

[0202] The liquid crystal layer 607 is configured by disposing the twotransparent substrates 601 and 602 so that the sides on which theorientation films are formed face each other, disposing a constant gapbetween the two transparent substrates 601 and 602 by sandwichingunillustrated spacers there between, sealing the area surrounding thisgap with a seal material 610 in a frame-shape, forming a space, andinjecting guest host liquid crystal into this space.

[0203] Here, the operation of the variable polarization selection member600 will be described with reference to FIGS. 17 and 18. FIGS. 17 and 18are partial schematic cross-sectional views showing an example of thevariable polarization selection member 600. The guest host liquidcrystal layer 607 is one in which dichroic dyes 6071 are added as aguest to nematic liquid crystal 6072. In the present example, liquidcrystal whose anisotropy is positive is used as the nematic liquidcrystal, and the orientation direction of the long axes of the liquidcrystal molecules is substantially horizontal with respect to thesubstrates 601 and 602 due to the orientation films 604 and 605, towhich a rubbing treatment has been administered, is an orientation inwhich there is no twist between the two transparent substrates 601 and602, i.e., is a homogenous orientation. A pretilt is added at this timeso that the orientation directions near the two transparent substrates601 and 602 are mutually parallel. It is preferable to add a 2° or moreangle of pretilt so that a reverse tilt does not occur. Here, a pretiltof about 4° is added.

[0204] Here, the dichroic dyes 6071 have a rod-like structure and aproperty in which they are oriented in a direction parallel to theliquid crystal molecules. For this reason, when, for example, theorientation of the liquid crystal molecules is changed from a horizontaldirection to a vertical direction with respect to the substrates, theorientation of the dichroic dyes is also similarly changed from thehorizontal direction to the vertical direction. Here, the guest hostliquid crystal material LA 121/4 (brand name) manufactured by MitsubishiChemical Corporation was used as the liquid crystal layer 607, and thethickness of the liquid crystal layer 607 was 5 μm.

[0205]FIG. 17 shows a state in which there is no difference in potentialbetween the transparent electrodes 603 and 606 respectively formed onthe two transparent substrates 601 and 602 and an electric field is notapplied to the liquid crystal layer 607, i.e., a state in which theswitching switch 600 a is in an OFF state. In this case, the nematicliquid crystal 6072 of the liquid crystal layer 607 is in an initialorientation state, i.e., has a homogenous orientation substantiallyhorizontal to the substrates (left-right direction of the page in thedrawing) and the dichroic dyes 6071 is also similarly orientated. Thedichroic dyes 6071 have an absorption polarization axis substantiallyparallel to the molecule axes and a property that strongly absorbs thepolarization component parallel to the molecule axes and virtually doesnot absorb the polarization component orthogonal thereto. For thisreason, when incident light 5000, which has various polarized wavesurfaces made incident from a substantially vertical direction withrespect to the transparent substrate surfaces, passes through the liquidcrystal layer 607, a linear polarization component Lp that has thevibration direction of an electric vector parallel to the molecule axesof the dichroic dyes 6071 is absorbed and a linear polarizationcomponent Ls that is orthogonal thereto is transmitted.

[0206]FIG. 18 shows a state in which a voltage is applied to thetransparent electrodes 603 and 606 respectively formed on the twotransparent substrates 601 and 602 and an electric field is applied tothe liquid crystal layer 607, i.e., a state in which the switchingswitch 600 a is in an ON state. In this case, the orientation directionof the molecule axes of the nematic liquid crystal 6072 is changed fromthe horizontal direction to the vertical direction with respect to thetwo transparent substrates 601 and 602, and the orientation direction ofthe dichroic dyes 6071 is changed in accompaniment therewith. For thisreason, the incident light 5000, which has various polarized wavesurfaces made incident from a substantially vertical direction withrespect to the transparent substrate surfaces, is transmitted virtuallywithout its polarization component being absorbed. At this time, in thepresent example, the voltage applied to the transparent electrodes 603and 606 of the transparent substrates 601 and 602 was ±30V, 60 Hz.

[0207] Therefore, by causing the orientation of the liquid crystalmolecules to match the polarization axis of the first linearpolarization, a variable polarization selection member, which isselectable between one of a state that absorbs the first linearpolarization component of the incident light and transmits the secondlinear polarization component, whose polarization axis is orthogonal tothat of the first linear polarization component, and a state thattransmits all polarization components, can be realized.

[0208] It should be noted that, it is preferable to administer, to thesurface of the variable polarization selection member 600, a treatmentthat suppresses regular reflection in order to suppress deterioration ofimage quality resulting from glare of outside light. However, that whichis important here is that, in order for the display device of theinvention to also function as a mirror, methods that reduce regularreflection components, such as forming minute recesses and projectionson the surface or forming a transparent resin layer includingtransparent particles on the surface, are not preferable as thetreatment for preventing regular reflectance of the variablepolarization selection member 600. The reason for this is because, whensuch a treatment is administered, although image display performance isimproved due to a reduction of glare, the problem arises that the imagereflected in the mirror becomes blurry and the performance of the mirrordeteriorates. Therefore, as the treatment for preventing regularreflectance of the variable polarization selection member 600, it ispreferable to form an antireflection film on the surface thereof. Wellknown technology can be used for the antireflection film. That is, amethod in which multilayers of several types of metal oxides havingdifferent optically designed refractive indexes are coated by vapordeposition, or a method in which a low refractive index material such asa fluorine compound is coated, can be used.

[0209]FIG. 19 are explanatory drawings of directions of axes of therespective members of the present example. It should be noted that thedisplay of the angle of each axis uses, as a reference, a position at 3o'clock in a horizontal direction of the image display surface, and isrepresented by an angle counterclockwise from here. As shown in FIG. 19,the transmission polarization axis of the linear polarization of theabsorbing polarization selection member (polarizing plate) 208 of the TNliquid crystal display panel 200 configuring the image display portion1000 is 135°. Therefore, the transmission polarization axis of thelinear polarization of the reflective polarization selection member 300is similarly 135°, the orientation directions of the liquid crystalmolecule long axes of the transparent substrate 401 and the transparentsubstrate 402 of the transmission polarization axis variable portion 400are 135° and 45°, respectively, the transmission polarization axis ofthe linear polarization of the reflective polarization selection member301 is 45°, and the orientation directions of the liquid crystalmolecule long axes of the transparent substrate 601 and the transparentsubstrate 602 of the variable polarization selection member 600 are both135°.

[0210] Next, the operation of the display device of Example 2 will bedescribed with reference to the drawings. FIGS. 20 and 21 are schematicstructural diagrams for describing the basic configuration and operationof the present display device.

[0211] In the present example, a case will be described in which, whenthe variable polarization selection member 600 is in an OFF state, thefirst linear polarization component (in the vertical direction of thepage in the drawings) is absorbed and the second linear polarizationcomponent (in the perpendicular direction of the page in the drawings),whose polarization axis is orthogonal to that of the first linearpolarization component, is transmitted, and when the variablepolarization selection member 600 is in an ON state, all polarizationcomponents are transmitted.

[0212] Also, a case will be described in which, when the transmissionpolarization axis variable portion 400 is in an OFF state, thepolarization axis of the incident linearly polarized light is changedwhen the incident linearly polarized light is transmitted therethroughand the incident linearly polarized light is changed to linearlypolarized light whose polarization axis is orthogonal to that of theincident linearly polarized light, and when the transmissionpolarization axis variable portion 400 is in an ON state, thepolarization axis is not changed.

[0213]FIG. 20 shows the case of the image display status. When thepresent display device is in the image display status, the transmissionpolarization axis variable portion 400 is in a state in which voltage isnot applied to the liquid crystal layer 407 configuring the transmissionpolarization axis variable portion 400, i.e., is in an OFF state. Thevariable polarization selection member 600 is also switched to an OFFstate.

[0214] As was already described, the image display portion 1000 isconfigured by the liquid crystal display panel 200 and the lightingsystem 100 disposed at the rear surface thereof. The first linearpolarization that is emitted from the lighting system 100 andtransmitted through the absorbing polarization selection member(polarizing plate) 208 of the liquid crystal display panel 200 isemitted as the image light 3001 from the image display portion 1000. Theimage light 3001 comprising the first linearly polarized light emittedfrom the image display portion 1000 is transmitted through thereflective polarization selection member 300 and made incident at thetransmission polarization axis variable portion 400.

[0215] The image light 3001 passing through the transmissionpolarization axis variable portion 400 is changed from the firstlinearly polarized light to the second linearly polarized light. Theimage light 3001 transmitted through the transmission polarization axisvariable portion 400 is made incident at the reflective polarizationselection member 301. Because the reflective polarization selectionmember 301 mirror-reflects the first linear polarization component buttransmits the second linear polarization component, the image light 3001that is changed to the second linearly polarized light by thetransmission polarization axis variable portion 400 is transmittedthrough the reflective polarization selection member 301 and is madeincident at the variable polarization selection member 600. When thedisplay device is in the image display status, the variable polarizationselection member 600 is in an OFF state, and of the light made incidentthereat, the first linear polarization component is absorbed but thesecond linear polarization component is transmitted. Therefore, theimage light 3001 is transmitted through the variable polarizationselection member 600 and is viewable to the viewer.

[0216] Although the outside light 3002 made incident from the viewerside (the left side in the drawing) to the display device isnon-polarized light, when the display device is in the image displaystatus, the variable polarization selection member 600 is in an OFFstate, the first linear polarization component of the light madeincident thereat is absorbed, and only the second linear polarizationcomponent is transmitted. When the outside light 3002 transmittedthrough the variable polarization selection member 600 is transmittedthrough the reflective polarization selection member 301, it is changedwhen transmitted through the transmission polarization axis variableportion 400, from the second linearly polarized light to the firstlinearly polarized light, transmitted through the reflectivepolarization selection member 300, proceeds toward the image displayportion 1000, and virtually does not return to the viewer side.

[0217] Therefore, in the image display status, a bright image can beobtained because the image light 3001 emitted from the image displayportion 1000 proceeds toward the viewer with virtually no loss.Moreover, because the outside light 3002 is virtually not reflected inthe display device, no deterioration of image quality resulting from theoutside light, such as a drop in the contrast ratio and glare, occurs.

[0218]FIG. 21 shows a case where the display device is in the mirrorstatus. When the display device is in the mirror status , thetransmission polarization axis variable portion 400 is switched to an ONstate in which voltage is applied to the liquid crystal layer 407configuring the transmission polarization axis variable portion 400. Thevariable polarization selection member 600 is also switched to an ONstate.

[0219] In this case also, the image light 3001 emitted from the imagedisplay portion 1000, and corresponding to the bright displaytransmitted through the reflective polarization selection member 300 ismade incident at the transmission polarization axis variable portion400. Because the image light 3001 transmitted through the transmissionpolarization axis variable portion 400 at this time is transmitted asthe first linearly polarized light without its polarization axis beingchanged, is reflected by the reflective polarization selection member301, and returns to the image display portion 1000, it is not viewableto the viewer.

[0220] With respect to the outside light 3002 proceeding from the viewerside to the display device, because the variable polarization selectionmember 600 is in an ON state and switched to a transparent state withrespect to most of the polarization components when the display deviceis in the mirror status, most of the outside light 3002 is transmittedthrough the variable polarization selection member 600. The outsidelight 3002 transmitted through the variable polarization selectionmember 600 is made incident at the reflective polarization selectionmember 301. Of the outside light 3002 made incident at the variablepolarization selection member 301, the second linear polarizationcomponent is transmitted through the reflective polarization selectionmember 301, and the first linear polarization component is reflected bythe reflective polarization selection member 301, again transmittedthrough the variable polarization selection member 600, and proceedstoward the viewer side. Of the outside light 3002 made incident at thereflective polarization selection member 301, the second linearpolarization component transmitted through the reflective polarizationselection member 301 is transmitted through the transmissionpolarization axis variable portion 400 without its polarization axisbeing changed, is reflected by the reflective polarization selectionmember 300, is again transmitted through the transmission polarizationaxis variable portion 400, through the reflective polarization selectionmember 301, and through the variable polarization selection member 600,and proceeds toward the viewer side.

[0221] In other words, in the case of the mirror status, because theimage light 3001 is reflected by the reflective polarization selectionmember 301 and returns to the image display portion 1000, it is notviewable to the viewer. Also, because most of the polarizationcomponents of the outside light 3002 are reflected by the firstreflective polarization selection member 300 and the reflectivepolarization selection member 301, the outside light 3002 functions asan extremely bright mirror.

[0222] It should be noted that, similar to Example 1, when the displaydevice is switched to the mirror status in the present example, thedisplay device can be configured so that the corresponding portion ofthe image display portion 1000 is switched to the dark display or sothat the lighting system 100 configuring the image display member isturned off in conjunction with the above-described operation. In thiscase, because the image light is not outputted from the image displayportion 1000, unnecessary stray light does not proceed to the viewer andthe performance of the mirror is not compromised. Particularly when thelighting system 100 is turned off, there is also the effect that powerconsumption can be reduced in the mirror status.

[0223] As described above, in the display device of the present example,the reflective polarization selection member 300 and the reflectivepolarization selection member 301 can be switched between an effectivelytransparent state and a state functioning as a mirror, due to thecontrol of the absorption of the polarized light by the variablepolarization selection member 600 and the control of the polarizationstate by the transmission polarization axis variable portion 400.Therefore, a bright image is obtained by switching the reflectivepolarization selection member 300 and the reflective polarizationselection member 301 to an effectively transparent state in the imagedisplay status. Moreover, because outside light is virtually notreflected in the display device even in an environment in which thesurrounding area is bright, deterioration of image quality, such asglare when a half mirror is used or a drop in the contrast ratioaccompanying glare, does not arise. In other words, switching betweenthe image display status and the mirror status can be realized withoutdeteriorating their mutual performance.

[0224] In particular, in the present example, when the display device isin the mirror status, because the variable polarization selection member600 is switched to the transparent state and most of the polarizationcomponents of the outside light are reflected by the reflectivepolarization selection member 300 and the reflective polarizationselection member 301, there is the effect that an extremely brightmirror of two times or more that of the display device of Example 1 canbe realized.

[0225] It should be noted that, in order to reduce interface reflectanceof each of the members configuring the display device, it is alsopossible to configure the device so that each member is optically bondedwith a transparent adhesive that combines their refractive indexes.

[0226] It should be noted that, in the above-described example, althougha liquid crystal whose anisotropy is positive was used for the nematicliquid crystal of the liquid crystal layer 607 of the variablepolarization selection member 600 and the orientation was a homogenousorientation, a liquid crystal whose anisotropy is negative may be usedas the nematic liquid crystal of the liquid crystal layer 607 and thedirection of the liquid crystal molecule long axes may have ahomeotropic orientation that becomes substantially perpendicular to thetransparent substrates in the initial state (a state in which anelectric field is not applied). In this case, although the orientationdirection of the liquid crystal molecule long axes changes from theperpendicular direction to a horizontal direction with respect to thetwo transparent substrates 601 and 602 when voltage is applied to thetransparent electrodes 603 and 606 of the two transparent substrates 601and 602 and an electric field is applied to the liquid crystal layer607, a slight pretilt angle may be added to the initial orientationstate of the liquid crystal so that the liquid crystal molecules areorientated in a constant direction.

[0227] When a liquid crystal whose anisotropy is negative is used as thenematic liquid crystal of the liquid crystal layer 607 and theorientation is a homeotropic orientation, because the direction of themolecule long axes of the nematic liquid crystal of the liquid crystallayer 607 becomes substantially perpendicular to the transparentsubstrates and the dichroic dye is also similarly oriented in the statein which there is no difference in potential between the transparentelectrodes 603 and 606 of the two transparent substrates 601 and 602 andan electric field is not applied to the liquid crystal layer 607, i.e.,the OFF state, the incident light from the outside is transmittedvirtually without being absorbed in the liquid crystal layer 607.

[0228] In the state in which voltage is applied to the transparentelectrodes 603 and 606 of the two transparent substrates 601 and 602 andan electric field is applied to the liquid crystal layer 607, i.e., inthe ON state, the orientation direction of the molecule long axes of thenematic liquid crystal changes from the perpendicular direction to thehorizontal direction with respect to the two transparent substrates 601and 602, and the orientation direction of the dichroic dye also changesto the horizontal direction in accompaniment therewith. The dichroic dyehas an absorption polarization axis substantially horizontal to themolecule axes and has the property that strongly absorbs thepolarization component parallel to the molecule axes and virtually doesnot absorb the polarized light component orthogonal thereto. For thisreason, when the incident light from the outside passes through theliquid crystal layer 607, the linear polarization component having thevibration direction of the electric vector in the direction parallel tothe molecule axes of the dichroic dye is absorbed and the linearpolarization component orthogonal thereto is transmitted.

[0229] In other words, by causing the orientation direction of theliquid crystal of the state in which an electric field is applied to theliquid crystal layer 607 to match the polarization axis of the firstlinear polarization, a variable polarization selection member, which isselectable between one of a state that absorbs the first linearpolarization component of the incident light and transmits the secondlinear polarization component, whose polarization axis is orthogonal tothat of the first linear polarization component, and a state thattransmits all polarization components, can be realized.

[0230] It should be noted that, in Example 2, a case was described inwhich the variable polarization selection member 600 was disposed at theviewer side of the reflective polarization selection member 301. Thevariable polarization selection member is an important member thatcontrols unnecessary reflection of outside light at the reflectivepolarization selection member 301 in the image display status andswitches to an effectively transparent state in the mirror status tocontribute to improving the brightness of the mirror. However, thepresent invention is not one that excludes a configuration in which thevariable polarization selection member 600 is not disposed at the viewerside of the reflective polarization selection member 301 whenconsideration is given various purposes. In this case, although thereare cases where outside light is reflected by the reflectivepolarization selection member 301 and the image becomes difficult toview in the image display status, an extremely high reflectance of 80%or more is obtained because there is no reflective polarizationselection member and there is no member obstructing the reflection ofoutside light by the reflective polarization selection member 301 in themirror status. This reflectance is a brightness comparable to a mirrorin which a thin film of aluminium is formed on a glass substrate, and amirror of a brightness equal to that of a common mirror can be realized.

[0231] (Size of the Mirror Region)

[0232] Here, a preferable size of the mirror region is determined in acase where the display device of Example 1 and Example 2 is chiefly usedfor a viewer to view his/her reflected face in the mirror status. Whenconsideration is given to the fact that the average height of an entireface of an adult male is 234.6 mm and that the average head width is156.4 mm (Ningen kogaku kijun suchi sushiki binran (“Handbook ofErgonomic Standard Numerical Values and Mathematical Formulas”), 1992,Gihodo Shuppan), a size with a height of 117.3 mm and a width of 78.2 mmor more is necessary as the size of the mirror in order for an entireface to be reflected in the mirror without the viewer changing his/herviewing position.

[0233] Switching between the image display status and the mirror statusis conducted by the transmission polarization axis variable portion 400in the display device of (Example 1) and by the transmissionpolarization axis variable portion 400 and the variable polarizationselection member 600 in (Example 2). Thus, in order to realize a mirrorregion having the above-described size, it is preferable for thetransparent electrodes 403 and 406 respectively formed on the twotransparent substrates 401 and 402 configuring the transmissionpolarization axis variable portion 400 and the transparent electrodes603 and 606 respectively formed on the two transparent substrates 601and 602 of the variable polarization selection member 600 to becontinuously formed, without omission, with respect to a region with atleast a height of 117.3 mm and a width of 78.2 mm or more. The reasonfor this is because, although the portions with the transparentelectrodes function as a mirror when the transparent electrodes are, forexample, divided and formed within this region range, the gaps betweenthe transparent electrodes do not function as a mirror, these gaps areviewed as stripes, and satisfactory performance as a mirror becomesunobtainable.

[0234] It should be noted that, when the display device of Example 1 andExample 2 is used in a portable instrument such as a mobile telephone ora PDA, sometimes the size of the display device itself is less than theabove-described mirror size of the 117.3 mm height and the 78.2 mmwidth. Thus, the mirror region can be configured so that a mirror of asize that does not reflect the entire face but is suited for the viewerto partially fix his/her makeup or check contact lenses in his/her eyesis obtained. In this case, the mirror region may be made to a size inwhich ¼ of the face is reflected in the mirror. Specifically, it ispreferable for the size of the mirror to have a height of 58.6 mm and awidth of 39.1 mm or more.

[0235] Therefore, it is preferable for the transparent electrodes 403and 406 respectively formed on the two transparent substrates 401 and402 configuring the transmission polarization axis variable portion 400and the transparent electrodes 603 and 606 respectively formed on thetwo transparent substrates 601 and 602 of the variable polarizationselection member 600 to be continuously formed, without omission, withrespect to a region with at least a height of 58.6 mm and a width of39.1 mm or more.

EXAMPLE 3

[0236] Although, in the display devices of Example 1 and Example 2, aliquid crystal display panel in which the lighting system was disposedat the underside thereof was used as the image display portion 1000emitting the first linear polarization as the image light, the presentinvention is not limited thereto.

[0237] A rear projection display device using a liquid crystal displaypanel as a two-dimensional optical switch element can be used as theimage display portion 1000 that emits the linearly polarized light asthe image light. Example 3 is an example that uses a rear projectiondisplay device as the image display portion 1000 of the display devicedescribed in Example 1. The same reference numerals will be given toparts that are the same as those in Example 1, and detailed descriptionwill be omitted.

[0238] As shown in FIG. 22, the display device is configured by atransmissive screen 703, a projection device 701, and a mirror 702, andstructured so that projection light 704 emitted from the projectiondevice 701 is irradiated onto the transmissive screen 703 via the mirror702. The transmissive screen 703 includes the reflective polarizationselection member 300, the transmission polarization axis variableportion 400, and the absorbing polarization selection member 500 ofExample 1.

[0239] A liquid crystal projection device that uses a liquid crystaldisplay panel as the two-dimensional optical switch element can be usedfor the projection device 701. A device that emits, as projection light,linear polarizations in which the polarization state of each color lightmatches is used for the projection device 701. Moreover, the image light704 emitted from the projection device 701 is configured so that itbecomes s-polarized light or p-polarized light with respect to thereflection surface of the mirror 702. The reason for this is because,when polarized light other than s-polarized light or p-polarized lightis made incident, the polarized state thereof changes because, withrespect to the light made incident on the reflection surface, a phasedifference is usually generated between the s-polarization component andthe p-polarization component with respect to the reflection surface.

[0240] A mirror in which a reflective metal such as silver or aluminiumis vapor deposited on optically isotropic transparent glass can be usedfor the mirror 702.

[0241] As shown in FIG. 23, the transmissive screen 703 has aconfiguration in which a Fresnel lens sheet 1402, a lenticular lenssheet 1401, the reflective polarization selection member 300, thetransmission polarization axis variable portion 400, and the absorbingpolarization selection member 500 are successively disposed. The Fresnellens sheet 1402 is an optical part that acts in the same manner as aconvex lens, and acts to widen the appropriate viewing range by bendingthe direction of the primary light ray from the projection device 701 tothe viewer side. The lenticular lens sheet 1401 acts to effectivelydistribute a limited projection light beam from the projection device701 to the viewing range of the viewer. Thus, a bright image isobtained.

[0242] An example of the lenticular lens sheet 1401 that can be used inthe present example will be described in FIGS. 24 and 25. The lenticularlens sheet 1401 has a configuration in which cylindrical lens-likelenses 1501 are plurally arranged in one direction and in which blackstripes 1502 are disposed at portions other than portions condensinglight, and has a configuration that controls drops in contrast ratiowith respect to outside light, ideally without any loss of reflectionlight, by using a focal point position of the lenses 1501 as a viewingsurface. Usually by arranging the lenticular lens sheet so that the busthereof is in a perpendicular direction with respect to the displaysurface, a wide viewing angle is obtained in the horizontal direction.

[0243] It should be noted that it is preferable to use, together withthe Fresnel lens sheet 1402 and the lenticular lens sheet 1401, a memberwhose birefringence is small, e.g., an injection-molded part usingacrylic resin, so that disturbance of the polarization of the projectionlight 704 from the projection device 701 becomes as small as possible.

[0244] As was already mentioned, because the reflective polarizationselection member 300 is an important member functioning as thereflection surface of the mirror, it can be made into a configurationadhered, with an adhesive, to a transparent substrate that has rigidity,is flat, and optically isotropic, e.g., an injection-molded acrylicresin plate with a thickness of about 3 mm, so that there is no warping.

[0245] The direction of each axis of the reflective polarizationselection member 300, the transmission polarization axis variableportion 400, and the absorbing polarization selection member 500 isdisposed so that, as mentioned in Example 1, the projection light 704emitted from the projection device 701 and made incident at thetransmissive screen 703 acts as the first linear polarization.

[0246] Next, the operation of the display device will be described.Here, a case will be described in which the absorbing polarizationselection member 500 absorbs the first linear polarization component andtransmits the second linear polarization component.

[0247] Because the display device is configured by the same members asin Example 1 other than using the rear projection display device for theimage display member, the operation is also the same. Namely, when thedisplay device is in the image display status, the image light 704emitted from the projection device 701 is reflected by the mirror 702and is made incident at the transmissive screen 703. The image light 704made incident at the transmissive screen 703 is transmitted through thereflective polarization selection member 300 while being effectivelywidened to the viewing range of the viewer by the action of the Fresnellens 1402 and the lenticular lens 1401, and is made incident at thetransmission polarization axis variable portion 400. When the displaydevice is in the image display status, the image light 704 passingthrough the transmission polarization axis variable portion 400 ischanged from the first linearly polarized light to the second linearlypolarized light, is transmitted through the absorbing polarizationselection member 500, and is viewable to the viewer.

[0248] Although outside light proceeding from the viewer side toward thedisplay device is non-polarized light, when the outside light istransmitted through the absorbing polarization selection member 500, thefirst linear polarization component is absorbed and only the secondlinear polarization component is transmitted. When the outside lighttransmitted through the absorbing polarization selection member 500 istransmitted through the transmission polarization axis variable portion400, it is changed from the second linearly polarized light to the firstlinearly polarized light, transmitted through the reflectivepolarization selection member 300, proceeds toward the projection device701 via the Fresnel lens 1402, the lenticular lens 1401, and the mirror702, and virtually does not return to the viewer side.

[0249] Therefore, in the image display status, a bright image can beobtained because the image light 704 that is emitted from the projectiondevice 701 and passes through the Fresnel lens 1402 and the lenticularlens 1401 proceeds toward the viewer with virtually no loss. Moreover,because the outside light is virtually not reflected in the displaydevice, deterioration of image quality resulting from the outside light,such as glare and a drop in the contrast ratio, does not occur.

[0250] When the display device is in the mirror status, the image light704 emitted from the projection device 701 is made incident at thetransmissive screen 703 via the mirror 702. The image light 704 madeincident at the transmissive screen 703 is transmitted through thereflective polarization selection member 300 while being effectivelywidened to the viewing range of the viewer by the action of the Fresnellens 1402 and the lenticular lens 1401, and is made incident at thetransmission polarization axis variable portion 400. When the displaydevice is in the mirror status, because the image light 704 transmittedthrough the transmission polarization axis variable portion 400 istransmitted as the first linearly polarized light without itspolarization axis being changed and is absorbed by the absorbingpolarization selection member 500, it is not viewable to the viewer.

[0251] Although outside light proceeding from the viewer side toward thedisplay device is non-polarized light, when the outside light istransmitted through the absorbing polarization selection member 500, thefirst linearly polarized light component is absorbed and only the secondlinearly polarized light component is transmitted and made incident atthe transmission polarization axis variable portion 400. The outsidelight made incident at the transmission polarization axis variableportion 400 is transmitted as the second linearly polarized lightthrough the transmission polarization axis variable portion 400 withoutits polarization axis being changed, and reaches the reflectivepolarization selection member 300. Because the reflective polarizationselection member 300 transmits the first linear polarization componentand mirror-reflects the second linear polarization component, theoutside light is reflected by the reflective polarization selectionmember 300. The outside light reflected by the reflective polarizationselection member 300 is transmitted as the second linearly polarizedlight through the transmission polarization axis variable portion 400without its polarization axis being changed, is also transmitted throughthe polarization selection member 500, and proceeds toward the viewer.

[0252] Therefore, in the mirror status, the image light 704 is absorbedby the absorbing polarization selection member 500 and does not reachthe viewer, and because ideally only half of the non-polarized light ofthe outside light made incident at the display device is reflected bythe reflective polarization selection member 300 and proceeds toward theviewer side, the outside light functions as a bright mirror.

[0253] It should be noted that, when the display device is switched tothe mirror status, the image of the projection device 701 is switched tothe dark display at the region corresponding to the region serving asthe mirror status. In this case, because virtually none of the imagelight from the projection device 701 leaks, unnecessary light does notproceed to the viewer. Thus, there is the effect that a mirror status inwhich is obtained a reflection image having a high contrast ratio can berealized.

[0254] Also, although a case was described in the above descriptionwhere the absorbing polarization selection member 500 transmits thesecond linear polarization component and absorbs the first linearpolarization component, a member may also be used in which the absorbingpolarization selection member 500 transmits the first linearpolarization component and absorbs the second linear polarizationcomponent. In this case, it can be made to function as a mirror when thepower consumption of the display device is 0.

[0255] Also, in the present example, the transmissive screen 703 wasconfigured so that the Fresnel lens sheet 1402, the lenticular lenssheet 1401, the reflective polarization selection member 300, thetransmission polarization axis variable portion 400, and the absorbingpolarization selection member 500 were successively disposed, as shownin FIG. 23. However, as an alternative to this configuration, thetransmissive screen 703 may be configured so that the Fresnel lens sheet1402, the lenticular lens sheet 1401, the reflective polarizationselection member 300, the transmission polarization axis variableportion 400, the reflective polarization selection member 301, and thevariable polarization selection member 600 are successively disposed, asshown in FIG. 26. In this case, the rear projection display device isused for the image display portion 1000 of display device described inExample 2, and an operation and action that are the same as those in thedescription of Example 2 are obtained.

[0256] Also, of the mirror function portion (the reflective polarizationselection member 300, the transmission polarization axis variableportion 400, the reflective polarization selection member 301, and thevariable polarization selection member 600) and the optical system (theFresnel lens sheet 1402 and the lenticular lens sheet 1401) configuringthe transmissive screen 703 of the present example, as a configurationin which the mirror function is detachable from the optical system, thedevice can be configured so that the mirror function portion is removedwhen the mirror function is unnecessary. Alternatively, it is alsopossible to configure a screen disposed independently of the mirrorfunction portion without including the image display portion and fit themirror function screen as needed to an optional display device.

EXAMPLE 4

[0257] A display device of Example 4 of the invention will be describedusing FIGS. 27 and 28. Example 4 is an example in which conductive metallinear patterns are formed at a pitch of over a thousand angstroms onthe transparent substrates 401 and 402 (see FIG. 16) of the displaydevice described in Example 2, and in which these metal linear patternsare also made to employ the functions of the reflective polarizationselection member 301 and the transparent electrode 403 and thereflective polarization selection member 300 and the transparentelectrode 406. Therefore, the same reference numerals will be given toparts that are the same as those in the above description, and detaileddescription will be omitted.

[0258] In Example 4, an aluminium metal linear pattern is formed at apitch of over a thousand angstroms on the transparent substrates 401 and402 of the transmission polarization axis variable portion 400. In thiscase, with respect to light made incident on the metal linear patterns,because the linear polarization component parallel to the longitudinaldirection of the lines of the metal linear pattern is reflected and thelinear polarization component of the direction orthogonal thereto istransmitted, the metal linear patterns function as the reflectivepolarization selection members. Also, because electric potential can bemade the same or substantially the same by electrically connecting partof these adjacent linear patterns, the metal linear patterns can also bemade to function as transparent electrodes that transmit specific linearpolarization components. In other words, the metal linear patternsemploy the functions of the reflective polarization selection membersand the transparent electrodes. It should be noted that the electricalconnection of adjacent linear patterns is conducted at places other thanthe mirror region, such as the peripheral edge portion or the like, sothat the functions of the reflective polarization selection members arenot adversely affected.

[0259] Here, as shown in FIG. 27, the transmission polarization axisvariable portion 400 includes the first transparent electrode 401, onthe entire surface of which are laminated and formed a metal linearpattern 311 and the orientation film 404 comprising a polyimide polymer,the second transparent electrode 402, on the entire surface of which aresimilarly laminated and formed a metal linear pattern 310 and theorientation film 405, and the liquid crystal layer 407.

[0260] The metal linear patterns 311 and 310 respectively formed on thetwo transparent substrates 401 and 402 are connected to a power sourcevia unillustrated wiring and a switching element, and are configured tobe selectable between one of a state in which voltage is not applied tothe metal linear patterns 311 and 310 and a state in which voltage isapplied. In other words, the metal linear patterns 311 and 310 areconfigured to be selectable between one of a state in which there is nodifference in potential between the metal linear patterns 310 and 310and an electric field is not applied to the liquid crystal layer 407 anda state in which voltage is applied to the metal linear patterns 311 and310 and an electric field is applied to the liquid crystal layer 407.Also, the longitudinal directions of the lines of the metal linearpatterns 310 and 311 are configured/disposed so that they are mutuallyorthogonal.

[0261] The liquid crystal layer 407 is configured by disposing the twotransparent substrates 401 and 402 so that the surfaces on which theorientation films 404 and 410 are formed face each other, disposing aconstant gap between the two transparent substrates 401 and 402 bysandwiching unillustrated spacers therebetween, sealing, in a frameshape, the area surrounding this gap with the seal material 410, forminga space, and injecting into this space nematic liquid crystal whosedielectric anisotropy is positive.

[0262]FIG. 28 are explanatory diagrams of the directions of the axes ofthe respective members of the present example. It should be noted thatthe display of the angle of each axis uses, as a reference, a positionat 3 o'clock in a horizontal direction of the image display surface, andis represented by an angle counterclockwise from here. As shown in FIG.28, the transmission polarization axis of the linearly polarized lightof the absorbing polarization selection member (polarizing plate) 208 ofthe TN liquid crystal display panel 200 configuring the image displayportion 1000 is 135°. Therefore, the transmission polarization axis ofthe linear polarization of the metal linear pattern 310 functioning asthe reflective polarization selection member is similarly 135°, theorientation directions of the liquid crystal molecule long axes of thetransparent substrate 401 and the transparent substrate 402 of thetransmission polarization axis variable portion 400 are 135° and 45°,respectively, the transmission polarization axis of the linearpolarization of the metal linear pattern 311 functioning as thereflective polarization selection member is 45°, and the orientationdirections of the liquid crystal molecule long axes of the transparentsubstrate 601 and the transparent substrate 602 of the variablepolarization selection member 600 are both 135°.

[0263] According to the above-described configuration, in the displaydevice of Example 4, because the metal linear pattern 310 fulfills thefunctions of the reflective polarization selection member 300 and theelectrode 406 of Example 2 and the metal linear pattern 311 fulfills thefunctions of the reflective polarization selection member 301 and theelectrode 403 of Example 2, the display device of Example 4 operates inthe same manner as the display device of Example 2 and the same effectsare obtained.

[0264] It should be noted that, as mentioned in Example 2, thereflective polarization selection members 300 and 301 are members thatfunction as reflection surfaces when the display device is switched tothe mirror status. For this reason, it is necessary to make the gapbetween the two as small as possible because parallax arises in theimages respectively reflected by the reflective polarization selectionmember 300 and the reflective polarization selection member 301 when thegap between the reflective polarization selection member 300 and thereflective polarization selection member 301 increases, and it ispractically preferable for the interval to be 0.11 mm or less. InExample 4, because there are only the liquid crystal layer 407 of aboutseveral μm and the thin films such as the orientation films 404 and 410that are less than 1 μm between the metal linear pattern 310 thatfunctions as the reflective polarization selection member 300 and themetal linear pattern 311 that functions as the reflective polarizationselection member 301, the gap between the two is less than 10 μm. Forthis reason, the effect that a high-definition mirror that is bright andhas no parallax can be realized is obtained.

[0265] Also, because the metal linear patterns 310 and 311 are formed ona flat substrate such as glass, there is also the effect that a mirrorthat is resistant to environmental changes, such as changes intemperature and humidity, and in which it is difficult for distortionresulting from environmental changes to arise can be realized.

[0266] Also, in the present invention, it suffices as long as the metallinear patterns 310 and 311 are patterns with which an even reflectioncan be obtained within the visible light range, and the specificstructure, pitch, pattern height, etc. of the linear patterns are notparticularly limited. Also, a metal linear pattern formed by chrome orsilver, other than the aluminium, may also be used.

EXAMPLE 5

[0267] In Examples 1 to 4, cases were described in which a mirrorfunction portion comprising the reflective polarization selection member300, the transmission polarization axis variable portion 400, and thepolarization selection member 500, or the mirror function portioncomprising the reflective polarization selection member 300, thetransmission polarization axis variable portion 400, the reflectivepolarization selection member 301, and the variable polarizationselection member 600, was disposed on the upper portion of the imagedisplay portion 1000 emitting the first linear polarization as the imagelight. In these cases, the image display portion 1000 is capable ofimage display even if the mirror function portion is not disposed, anddepending on the intended use of the instrument, the mirror functionportion is made detachable so that the mirror function portion isremoved when the mirror function portion is unnecessary, wherebyconvenience can be improved.

[0268] However, the present invention is not limited to these cases. Inother words, the invention may have a configuration in which imagedisplay is possible when there is the mirror function portion, or aconfiguration in which a partial configuration of the mirror functionportion and the image display member is shared.

[0269] A display device of Example 5 will be described using FIG. 29.Because there are many portions in Example 5 that are common to those ofExample 1 (e.g., see FIG. 8), the same reference numerals will be givento members that are the same as those in Example 1 and detaileddescription will be omitted.

[0270] The present display device is one in which, in the display devicedescribed in Example 1, a lighting system that can irradiate, timedivisionally, the three primary colors of red, green, and blue is usedas the lighting system 100 and the absorbing polarization selectionmember (polarizing plate) 208 of the viewer side is removed from theimage display portion 1000. Therefore, when the mirror function portioncomprising the reflective polarization selection member 300, thetransmission polarization axis variable portion 400, and the absorbingpolarization selection member 500 is removed, the liquid crystal displaypanel 200 of the present example cannot display a clear image.

[0271] The liquid crystal display panel 200 of the present example isone in which, in the liquid crystal display panel 200 of Example 1, theabsorbing polarization selection member (polarizing plate) 208 isremoved, the color filter is eliminated, and in which it is possible toincrease the speed of the response of the liquid crystal so that it isable to correspond to a field-sequential color display system.

[0272] Technical details of field-sequential color display systems aredescribed in, for example, JP-A-5-19257 and JP-A-11-52354. The presentsystem is one that irradiates illumination light of the three primarycolors onto the liquid crystal display panel at the time sharing andrealizes display of a color image by driving the liquid crystalsynchronously therewith. That is, in the liquid crystal display panel,because it is necessary to successively display three subframescorresponding to the three primary colors in order to conduct display ofone frame, it is necessary for the liquid crystal to respond at a higherspeed. In order to quicken the response of the liquid crystal so that itcan correspond to a field-sequential color display system, e.g., when aTN mode is used, liquid crystal having a large birefringence An is usedin order to satisfy the conditions of the above-described waveguide andthe thickness of the liquid crystal layer 207 is thinly configured toabout 2 μm.

[0273] It should be noted that, although the case of the TN mode will bedescribed below in the present example, the liquid crystal display panelof the present invention is not limited to the above-describedconfiguration as long as it has a configuration in which responsecharacteristics corresponding to a field-sequential color display systemare obtained.

[0274] The lighting system 100 is configured by a waveguide 193comprising a transparent medium, a light source 190 that emits the threeprimary colors of red, green, and blue and is disposed at an end surfaceof the waveguide 193, a polarization maintenance reflection sheet 192disposed at an underside of the waveguide 193, and a polarizationmaintenance diffusion portion 191 disposed at the front side of thewaveguide 193.

[0275] An LED (Light Emitting Diode) in which three chips are integratedthat emit respective color lights of the three primary colors can beused as the light source 190 emitting light of the three primary colorsof red, green, and blue. Such an LED is sold by Nichia Corporation.

[0276] The waveguide 193 is configured by a transparent acrylic resin,has a configuration that traps thereinside light made incident from theend surface by total reflection, and is disposed at the underside (sideopposite from the liquid crystal display panel 200) with an inclinedreflection surface 194 that is configured by plural steps or unevensurfaces including minute inclined surfaces that radiate light towardthe liquid-crystal display panel 200 by changing the reflection angle ofthe light propagated through the inside. This is for maintaining thepolarized state of the light made incident at the waveguide 193 from theliquid crystal display panel 200 for a reason described later.

[0277] Although it is preferable for the inclined reflection surface 194to be a metal thin film of aluminium, silver or the like or a mirrorreflection surface by a derivative multilayer film, it is not limited tothese, and is a surface in which a necessary reflective function issatisfied by a difference in birefringence between the air and theacrylic resin even if such a special reflective member is not added.

[0278] Here, the average pitch of the inclined reflection surface 194 is200 μm, the average height is 10 μm, and the average angle ofinclination is 410. It should be noted that the evenness of the lightemitted from the waveguide 193 may be raised by continuously changingthe height of the inclined reflection surface 194 so that it is low nearthe light source 190 and high at a place distant from the light source190, or by continuously changing the pitch or angle of inclination ofthe inclined reflection surface 194 by the distance from the lightsource 190, or by thinning the thickness of the waveguide 193 as it isbecomes distanced from the light source 190.

[0279] It should be noted that the shape of the waveguide 193 is notlimited to the present shape as long as it substantially maintains thepolarization state of the light made incident at the waveguide 193 fromthe liquid crystal display panel 200 side.

[0280] The polarization maintenance reflection sheet 192 is a sheet inwhich a reflection surface that maintains the polarization state isformed on a substrate material such as a glass plate, a resin plate, ora resin film, and includes the function of again reflecting light thathas returned from the liquid crystal display panel 200 side to thelighting system 100 toward the liquid crystal display panel 200 sidewhile maintaining the polarization state thereof. The reflection surfacemaintaining the polarization state described here is a reflectionsurface that reflects linearly polarized light as the same linearlypolarized light and reflects a circular polarization as a circularpolarization in which the rotation direction thereof is reversed, withrespect to at least perpendicularly incident light. Specifically, asurface in which a metal thin film of Al or Ag is adhered to a substratematerial, or a mirror reflection surface resulting from a derivativemultilayer film configured so that a high reflectance is obtained withrespect to the waveband of the light source light, is used as thereflection surface.

[0281] The polarization maintenance diffusion portion 191 is for makingeven the in-plane luminance distribution and emission angle distributionof the light emitted from the waveguide 193, and for substantiallymaintaining the polarization state of the light passing therethrough. Amember in which plural spherical transparent beads are closely lined upin a sheet and fixed with a transparent resin to an optically isotropicsubstrate material, a hologram diffusion plate formed on an opticallyisotropic transparent substrate material, or the LCG (light controlglass) described in SPIE, Vol. 1536, Optical Materials Technology forEnergy Efficiency and Solar Energy Conversion X (1991), pp. 138-148, canbe used as the polarization maintenance diffusion portion 191.

[0282]FIG. 30 are explanatory diagrams of the directions of the axes ofthe respective members of the present example. As is illustrated, when aTN liquid crystal display panel is used as the liquid crystal displaypanel 200, the transmission polarization axis of the linear polarizationof the polarizing plate 209 is ordinarily 45° or 135° (in the presentexample, 45°) in order to obtain horizontal direction symmetry ofviewing angle characteristics. The liquid crystal orientation axis ofthe transparent substrate 202 and the liquid crystal orientation axis ofthe transparent substrate 201 are 45° and 135°, respectively, thetransmission polarization axis of the linear polarization of thereflective polarization selection member 300 is 135°, the orientationdirections of the liquid crystal molecule long axes of the transparentsubstrate 401 and the transparent substrate 402 of the transmissionpolarization axis variable portion 400 are 135° and 45°, respectively,and the transmission polarization axis of the linear polarization of theabsorbing polarization selection member 500 is 45°.

[0283] Next, the operation of the present example will be described. Thelight emitted from the light source 190 is made incident at thewaveguide 193 and is propagated through the waveguide 193 whilerepeating total reflection. Of the light propagated through thewaveguide 193, the traveling direction of the light reaching theinclined reflection surface 194 is changed and the light is emitted fromthe surface side of the waveguide 193. After the emission angledistribution and in-plane luminance distribution of the light emittedfrom the waveguide 193 have been made even by the polarizationmaintenance diffusion portion, the light is irradiated onto the liquidcrystal display element 200.

[0284] Of the light irradiated on the liquid crystal display panel 200,the linearly polarized light transmitted through the polarizing plate209 passes through the liquid crystal layer 207 and is made incident atthe reflective polarization selection member 300, but the polarizationstate of the light transmitted through the liquid crystal layer 208 canbe changed by the voltage applied to the liquid crystal layer 207. Forthis reason, voltage corresponding to the image information transmittedfrom the image information generating portion is applied to thetransparent electrodes 203 and 205 on the transparent substrates 202 and201 and an electric field is applied to the liquid crystal layer 207,whereby the polarization state of the light passing through the liquidcrystal layer 207 is changed and the light amount transmitted throughthe reflective polarization selection member 300 is controlled, wherebyan optical image comprising the linearly polarized light can be formed.That is, the reflective polarization selection member 300 of the presentexample employs the function of the absorbing polarization selectionmember (polarizing plate) 208 disposed at the viewer side of the liquidcrystal display panel 200 in Example 1.

[0285] The image light transmitted through the reflective polarizationselection member 300 is made incident at the transmission polarizationaxis variable portion 400. When the display device is in the imagedisplay status, the transmission polarization axis variable portion 400is in a state in which voltage is not applied to the liquid crystallayer 407 configuring this, i.e., an OFF state.

[0286] Here, when the linear polarization component transmitted throughthe reflective polarization selection member 300 is the first linearpolarization component and the linear polarization component whosepolarization axis is orthogonal thereto is the second linearpolarization component, the image light passing through the transmissionpolarization axis variable portion 400 is changed from the firstlinearly polarized light to the second linearly polarized light. Theimage light transmitted through the transmission polarization axisvariable portion 400 is made incident at the absorbing polarizationselection member 500. Because the absorbing polarization selectionmember 500 absorbs the first linear polarization component and transmitsthe second linear polarization component, the image light 3001 that ischanged to the second linearly polarized light by the transmissionpolarization axis variable portion 400 is transmitted through theabsorbing polarization selection member 500 and is viewable to theviewer.

[0287] When the display device is in the mirror status, the transmissionpolarization axis variable portion 400 applies an electric field to theliquid crystal layer 407 configuring this and is switched to an ONstate. Because there is no absorbing polarization selection member(polarizing plate) 208 disposed as the absorbing polarization selectionmember in the above example in the display device in this case, theimage light leaks to the viewer side when the lighting system 100 isturned on, whereby the contrast ratio of the reflection image drops andan easy-to-view mirror cannot be realized. Therefore, the lightingsystem 100 is turned on in the mirror status. In the case of the presentexample, because it can be turned on and off at a high speed bydisposing the LED as the light source 190 of the lighting system 100,the mirror status and the image display status are switchable at a highspeed to the extent that it does not cause the viewer to feel stress.

[0288] When the outside light proceeding from the viewer side to thedisplay device is transmitted through the absorbing polarizationselection member 500, the first linear polarization component isabsorbed and only the second linear polarization component istransmitted and made incident at the transmission polarization axisvariable portion 400. The outside light made incident at thetransmission polarization axis variable portion 400 is transmittedthrough the transmission polarization axis variable portion 400 as thesecond linear polarization without its polarization axis being changedand reaches the reflective polarization selection member 300. Becausethe reflective polarization selection member 300 transmits the firstlinear polarization component and mirror-reflects the second linearpolarization component, the outside light 3002 is reflected by thereflective polarization selection member 300. The outside light 3002reflected by the reflective polarization selection member 300 istransmitted through the transmission polarization axis variable portion400 as the second linear polarization without its polarization axisbeing changed, is further transmitted through the absorbing polarizationselection member 500, and proceeds toward the viewer.

[0289] Therefore, in the display device of the present example, becausethe lighting system is turned off in the mirror status, the image lightdoes not reach the viewer, and because ideally half of the non-polarizedlight of the outside light is reflected by the reflective polarizationselection member 300 and proceeds toward the viewer side, the lightfunctions as a bright mirror.

[0290] In addition, there are the following unique effects in thepresent example.

[0291]FIG. 31 is a diagram for describing the unique effects of thepresent example. Here, when the linear polarization componenttransmitted through the reflective polarization selection member 300 isthe first linear polarization component and the linear polarizationcomponent whose polarization axis is orthogonal thereto is the secondlinear polarization component, the polarizing plate 209 transmits thesecond linear polarization component.

[0292] In the display device, as described above, of the lightirradiated on the liquid crystal display panel 200 from the lightingsystem 100, the second linearly polarized light (direction perpendicularto the page in the drawing) transmitted through the polarizing plate 209passes through the liquid crystal layer 207 and is made incident at thereflective polarization selection member 300. At this time, thepolarization state of the light transmitted through the liquid crystallayer 207 is modulated in correspondence to the image information, andthe light 3100 passing through the bright display region is changed fromthe second linearly polarized light to the first linearly polarizedlight, transmitted through the reflective polarization selection member300, and proceeds toward the viewer.

[0293] Because the light 3101 passing through the dark display region ismade incident at the reflective polarization selection member 300 as thesecond linearly polarized light, it is reflected by the reflectivepolarization selection member 300 and does not reach the viewer. Thelight 3101 reflected by the reflective polarization selection member 300is again transmitted through the liquid crystal layer 207 and thepolarizing plate 209 as the second linearly polarized light and returnsto the lighting system 100. At this time, the polarization maintenancediffusion portion, the waveguide, and the polarization maintenancereflection sheet 192 configuring the lighting system 100 substantiallymaintain, transmit, or reflect the polarization state of the lightreturning from the liquid crystal display element 200 side. For thisreason, because the light 3101 reflected by the lighting system 100 andproceeding to the liquid crystal display panel 200 generally becomes thesecond linearly polarized light, it is made incident at the liquidcrystal layer 207 virtually with out being absorbed by the polarizingplate 209. Of the light 3101 made incident at the liquid crystal layer207, the light made incident at the bright display region is changedfrom the second linearly polarized light to the first linearly polarizedlight transmitted through the reflective polarization selection member300, proceeds toward the viewer side, and can be effectively utilized asthe image light.

[0294] In other words, because the light made incident at the darkdisplay region is initially reflected by the reflective polarizationselection member 300, it does not become image light. However, the lightreflected by the reflective polarization selection member 300 proceedsto the lighting system 100, is reflected in the lighting system 100 in astate in which its polarization state is substantially maintained, andagain proceeds to the liquid crystal display panel 200. For this reason,reuse of light is conducted in a state in which there is not large loss,and the brightness of the bright display region is improved.

[0295] Also, although light transmittance of a color filter is usuallyabout 25%, which is low, because a color filter is not used in thepresent example, reuse of light is conducted more efficiently.

[0296] Here, in liquid crystal display panels, there is usually nodifference in the luminance of the white display between a case wherethe entire screen is switched to a white display and a case where aportion is switched to a white display. With a CRT (Cathode Ray Tube),it is said that the white display can be brightened by about four timesin a case where a 15% portion of the screen is switched to a whitedisplay with respect to a case where the entire screen is switched to awhite display. When a high luminance image is partially displayed with,for example, sunlight, this appears as a difference in image quality inwhich a more vivid image is obtained with a CRT than a liquid crystaldisplay panel.

[0297] In the display device of the present example, because thebrightness of the bright display region can be improved by reusing thelight made incident at the dark display region, the white display can bebrightened in a case where a portion is switched to a white display incomparison with a case where the entire screen is switched to a whitedisplay. Therefore, a vivid image that is close to that of a CRT isobtained.

[0298] Moreover, the following effects are obtained when the displaydevice is used as a display portion in a portable instrument such as amobile telephone. Although the display device functions as a colordisplay device resulting from a field-sequential color display systemwhen the lighting system is turned on, it can be made to function as areflective liquid crystal display panel of a bright monochrome displaybecause there is no color filter when the lighting system is turned off.Here, in the case of the color display, although it is necessary todisplay at least three subframes of red, green, and blue in order toconduct display of one frame, in the case of the monochrome display, thedrive frequency can be made ⅓ or lower because it is not necessary todispose a subframe. Because the drive frequency can be lowered to ⅓ orlower and the power consumption can be largely reduced, the powerconsumption of the monochrome display state can be largely reduced whena drive frequency switch portion is disposed and the drive frequency isswitched between the color display state and the monochrome displaystate.

[0299] In other words, when the display device is used as a displayportion in a portable instrument, the lighting system is turned on whenthe device is in a use state and the device is switched to the colordisplay state, whereby a vivid, bright, high-definition image isobtained, and, when the device is standing by, the lighting system isturned off, the drive frequency is lowered, and the device is switchedto the monochrome display state, whereby power consumption can begreatly lowered. For this reason, use time resulting from a battery inthe portable instrument can be lengthened by lengthening the standbytime of, for example, a mobile telephone.

[0300] Moreover, these effects are established as described abovebecause it is possible to switch between the image display status andthe mirror status without their mutual performance being deteriorated.Also, in the present example, the metal linear patterns are formed onthe transparent substrates at the viewer side of the liquid crystaldisplay panel and parts of the respective patterns are electricallyconnected, whereby metal linear patterns may be made to employ thefunctions of the transparent electrodes and the reflective polarizationselection member.

EXAMPLE 6

[0301] Another example of the invention will be described below on thebasis of the drawings.

[0302] A display device disposed with a function for switching to amirror status of Example 6 of the invention will be described using FIG.32. The display device is one in which a reflective liquid crystal panel3000 is used as the image display portion 1000 in Example 1. The samereference numerals will be given to members that are the same those ofthe above-described examples and detailed description will be omitted.

[0303] The display device of Example 6 includes the reflective liquidcrystal element 3000, and the reflective liquid crystal element includesa transparent substrate 3030, a reflective substrate 3100 disposed witha reflective portion, and a liquid crystal layer 3130 that is sealed ina space formed by adhering these two substrates via spacers such asbeads and sealing the substrates with a frame-like seal member. Also, aphase-difference plate 3020, the reflective polarization selectionmember 300, the transmission polarization axis variable portion 400, andthe absorbing polarization selection member 500 are superposed anddisposed on the transparent substrate 3030.

[0304] A flat insulating substrate such as glass or a polymer film isused as the reflective substrate 3100, and a 0.7 mm-thick glasssubstrate is used here. A switching element 3110 comprising a scanningelectrode, a signal electrode, and, for example, a TFT (Thin FilmTransistor) disposed at the intersection of these, an insulating film3090 formed on an upper portion of these, and a pixel electrode 3070that is formed on the insulating layer and is segmented in a matrixelectrically connected to the switching element via a through hole 3120opening to the insulating layer 3090 are disposed on the reflectivesubstrate 3100.

[0305] The pixel electrode 3070 comprises a metal with a highreflectance, such as aluminium or silver, and functions as a diffusereflecting reflective portion due to minute recess portion or projectingportion shapes formed on the insulating layer 3090. An orientation film3060 comprising a polyimide polymer is formed on the entire surface ofthe upper layer of the pixel electrode 3070, and a surface treatment isadministered to the surface thereof by rubbing.

[0306] An optically isotropic, flat, transparent insulating substratesuch as glass or a polymer film can be used as the transparent substrate3030, and a 0.7 mm-thick glass substrate is used here. A color filter3040 is formed at a position on the transparent electrode 3030corresponding to the pixel electrode 3070 of the reflective substrate3100. The color filter 3040 is one in which three types of color filtersincluding transmission spectrums respectively corresponding to the threeprimary colors of red, green, and blue are alternatingly repeated anddisposed at a position corresponding to the pixel electrode 3070.

[0307] Also, a black matrix may be formed at positions corresponding tothe spaces between the pixels of the color filter 3040 to suppress lightleaking from the spaces between the pixels. A transparent electrode 3050comprising ITO is formed on the entire surface of the upper layer of thecolor filter 3040 via an unillustrated overcoat layer, an orientationfilm 3210 comprising a polyimide polymer is formed on the entire surfaceof the upper layer of the transparent electrode 3050, and a surfacetreatment is administered to the surface thereof by rubbing.

[0308] The transparent substrate 3030 and the reflective substrate 3100are adhered together so that the sides on which the transparentelectrode 3050 and the reflective electrode 3070 are formed face eachother. At this time, bead spacers are dispersed between the substratesand the area surrounding the portion corresponding to the displaysurface of both substrates is sealed with a frame-like seal member,whereby a space including a constant gap is formed.

[0309] The liquid crystal layer 3130 is configured by injecting andsealing, in the gap between the substrates 3030 and 3100, a liquidcrystal composition in which a small amount (0.1 to 0.2%) of a chiralagent is added to nematic liquid crystal whose anisotropy is positive.The And of the liquid crystal layer 3130 is 0.365 μm. The orientationdirection of the liquid crystal molecule long axes of the liquid crystallayer 3130 is defined by the surface treatment (orientation treatment)administered to the orientation film 3210 and the orientation film 3060formed on the transparent substrate 3030 and the reflective substrate3100, and is continually twisted only by a predetermined angle betweenthe two substrates.

[0310] The phase-difference plate 3020 is laminated on the transparentsubstrate 3030. A uniaxially stretched polymer film, such aspolycarbonate, polysulfone, or polyvinyl alcohol, can be used as thephase-difference plate 3020. Here, a phase-difference plate comprisingpolycarbonate whose Δnd is 0.18 μm is used as the phase-difference plate3020.

[0311] The transparent substrate 3030, the phase-difference plate 3020,the reflective polarization selection member 300, the transmissionpolarization axis variable portion 400, and the absorbing polarizationselection member 500 are respectively adhered with an acrylic adhesiveso as to be optically bonded.

[0312]FIG. 33 are diagrams showing the directions of the axes of therespective members of the display device when seen from the viewer side.The angle of each axis uses, as a reference, a position at 3 o'clock ina horizontal direction of the image display surface, and is representedby an angle counterclockwise from here. As shown in FIG. 33, in thedisplay device, the liquid crystal orientation axis of the reflectivesubstrate 3100 is 295°, the azimuth of the liquid crystal orientationaxis at a side of transparent substrate 3030 is 65°, the lag axis of thephase-difference plate 3020 is 135°, the transmission polarization axisof the linear polarization of the reflective polarization selectionmember 300 is 30°, the liquid crystal orientation axis of thetransparent substrate 402 is 30°, the liquid crystal orientation axis ofthe transparent substrate 401 is 120°, and the transmission polarizationaxis of the linear polarization of the absorbing polarization selectionmember 500 is 120°.

[0313] Next, the operation of the display device will be described usingthe drawings. It should be noted that, in the present example, similarto Example 1, the linear polarization component transmitted through thereflective polarization select ion member 300 is the first linearpolarization component and the linear polarization component whosepolarization axis is orthogonal thereto is the second linearpolarization component.

[0314]FIG. 34 shows a case where the display device is in the mirrorstatus. In this case, although the outside light 3002 proceeding towardthe display device from the viewer side is non-polarized light, when itis transmitted through the absorbing polarization selection member 500,the first linear polarization component is absorbed, and only the secondlinear polarization component is transmitted and made incident at thetransmission polarization axis variable portion 400. The outside light3002 made incident at the transmission polarization axis variableportion 400 is transmitted through the transmission polarization axisvariable portion 400 as the second linear polarization without itspolarization axis being changed, and reaches the reflective polarizationselection member 300. Because the reflective polarization select ionmember 300 transmits the first linear polarization component andmirror-reflects the second linear polarization component, the outsidelight 3002 is reflected by the reflective polarization selection member300. The outside light 3002 reflected by the reflective polarizationselection member 300 is transmitted through the transmissionpolarization axis variable portion 400 as the second linear polarizationwithout its polarization axis being changed, is further transmittedthrough the absorbing polarization selection member 500, and proceedstoward the viewer.

[0315] In other words, when the display device is in the mirror status,the outside light 3002 is reflected by reflective polarization selectionmember 300 without reaching the reflective liquid crystal element 3000,proceeds toward the viewer side, and functions as a bright mirror.

[0316] It should be noted that, when the display device is switched tothe mirror status, the reflective liquid crystal element 3000 can beswitched to a non-display state so that energy is not wastefullyconsumed.

[0317]FIG. 35 and FIG. 36 show a case where the display device is in theimage display status. The image display status will be also describedwith reference to FIG. 32. In this case, although the outside light 3002proceeding from the viewer side (left side in the drawing) toward thedisplay device is non-polarized light, when it is transmitted throughthe absorbing polarization selection member 500, the first linearpolarization component is absorbed, and only the second linearpolarization component is transmitted. When the outside light 3002transmitted through the absorbing polarization selection member 500 istransmitted through the transmission polarization axis variable portion400, it is changed from the second linearly polarized light to the firstlinearly polarized light, transmitted through the reflectivepolarization selection member 300, and made incident at the reflectiveliquid crystal element 3000. The first linearly polarized light madeincident at the reflective liquid crystal element 3000 is transmittedthrough the phase-difference plate 3020 and the liquid crystal layer3130, is reflected by the pixel electrode 3070, again passes through theliquid crystal layer 3130 and the phase-difference plate 3020, and ismade incident at the reflective polarization selection member 300. Atthis time, the polarization state of the light transmitted through theliquid crystal layer 3130 is changed by voltage applied to the liquidcrystal layer 3130.

[0318] Here, the switching element 3110 is connected to the pixelelectrode 3070 via the throughhole 3120 and switches the voltage appliedto the pixel electrode 3070, whereby the voltage applied to the liquidcrystal layer 3130 sandwiched between the transparent electrode 3050 andthe pixel electrode 3070 can be controlled per pixel. Therefore, byapplying a voltage corresponding to the image information to thetransparent electrode 3050 and the pixel electrode 3070 and applying apredetermined voltage to the liquid crystal layer 3130, the polarizationstate of the light passing through the liquid crystal layer 3130 iscontrolled, the light amount transmitted through the reflectivepolarization selection member 300 is controlled, and an optical imagecan be formed.

[0319]FIG. 35 illustrates the case of the bright display. In theconfiguration of the present example, when a voltage is not applied tothe liquid crystal layer 3130, the light made incident at the reflectiveliquid crystal element 3000 is reflected as the first linearly polarizedlight, is again transmitted through the reflective polarizationselection member 300, and is made incident at the transmissionpolarization axis variable portion 400. When the light made incident atthe transmission polarization axis variable portion 400 is transmittedtherethrough, it is changed from the first linearly polarized light tothe second linearly polarized light, transmitted through the absorbingpolarization selection member 500, proceeds toward the viewing side, andbecomes the bright display.

[0320]FIG. 36 shows the case of the dark display. In the configurationof the present example, when the predetermined voltage is applied to theliquid crystal layer 3130, the first linearly polarized light madeincident at the reflective liquid crystal element 3000 is reflected bythe reflective liquid crystal element 3000 and emitted, at which time itbecomes the second linearly polarized light and is again made incidentat the reflective polarization selection member 300. The second linearlypolarized light that is again made incident at the reflectivepolarization selection member 300 is reflected by the reflectivepolarization selection member 300 and again made incident at thereflective liquid crystal element 3000. The second linearly polarizedlight made incident at the reflective liquid crystal element 3000 isreflected by the reflective liquid crystal element 3000 and emitted, atwhich time it becomes the first linearly polarized light.

[0321] However, at this time, the three types of color filters 3040including respectively different transmission spectrums corresponding tothe three primary colors of red, green, and blue are alternatinglyrepeated and formed on the transparent substrate 3030 of the reflectiveliquid crystal element 3000. Therefore, for example, as is illustrated,the light initially made incident at the reflective liquid crystalelement 3000 is made incident at the green color filter 3040G,transmitted, and made incident at the blue color filter 3040B in thesecond incidence, whereby the light is virtually absorbed and becomesthe dark display. Also, even if the light made incident at thereflective liquid crystal element 3000 passes through a color filter ofthe same color, it passes twice along a reciprocal path so that itpasses through the color filter for a total of four times, whereby thedark display is obtained. That is, in the configuration of the presentexample, the color filters are used as members for improving thedarkness of the display.

[0322] In order to realize a sufficiently dark display, it is preferableto pass through the color filters of the different colors when it passesthrough the color filters four times. For this reason, it is preferablefor the arrangement of the color filters to be made into a deltaarrangement and not a stripe, in order for the colors of the colorfilters that are vertically and left-right adjacent to be as differentas possible.

[0323] Also, because the thicker the transparent substrate 3030 of thereflective liquid crystal element 3000 is, the easier it becomes for thelight reflected by the reflective polarization selection member 300 topass through different positions of the reflective liquid crystalelement 3000 and pass through the color filters of the different colors,it is preferable to thicken the transparent substrate 3030 as much aspossible within a practical range.

[0324] As described above, according to the display device of Example 6,the reflective polarization selection member 300 is switchable betweenan effectively transparent state and a state functioning as a mirror,due to the control of the polarization state by the transmissionpolarization axis variable portion 400. Therefore, in the image displaystatus, the reflective polarization selection member 300 is switched tothe effectively transparent state, whereby a bright image is obtained.Moreover, even in an environment in which the surrounding area isbright, deterioration of image quality, such as glare in a case where ahalf mirror is used, and a drop in the contrast ratio and a drop in thebrightness of the image light accompanying glare, does not arise. Inother words, switching between the image display status and the mirrorstatus can be realized without deteriorating their mutual performance.

[0325] Incidentally, in the present example, a case was described wherea polarizing plate functioning as the absorbing polarization selectionmember is not disposed at the reflective liquid crystal panel 3000. Thisis because it is important to reduce as much as possible members thatabsorb light in order to improve the brightness of the image displaystatus. In particular, it is because it is a situation in which it isnot allowable for an image to become darker due to the mirror functionportion comprising the absorbing polarization selection member, thetransmission polarization axis variable portion, and the reflectivepolarization selection member, because an image is originally dark in areflective liquid crystal display panel capable of color display.Therefore, a polarizing plate may be disposed at the reflective liquidcrystal element 3000 if the purpose is one in which the frequency of useis high in a place where the outside light is strong, such as outdoors.

[0326] Moreover, if the polarizing plate is one having a hightransmittance, in which the transmittance with respect to thepredetermined linearly polarized light component is near 100%, it ispreferable that the brightness of the image is virtually not reducedeven if the transmission polarization axis of the polarizing plate iscombined with the transmission polarization axis of the reflectivepolarization selection member and the polarizing plate is disposed atthe reflective liquid crystal element 3000, i.e., between the reflectivepolarization selection member 300 and the transparent substrate 3030. Inthis case, although an image display of a sufficient contrast ratio isnot possible with a single reflective liquid crystal panel because thedegree of polarization of a polarizing plate with a high transmittanceis usually low, there are no problems with display performance when apolarizing plate having a high degree of polarization is used as theabsorbing polarization selection member 500. Rather, in the case of theimage display, there is the advantage that a darker dark display isrealized and an image display with a high contrast ratio can berealized.

[0327] In other words, in a case where a reflective liquid crystaldisplay panel in which a reflective portion is internally housed withina substrate is used as the image display member, when a polarizing platehaving a high degree of polarization is used for the absorbingpolarization selection member and a polarizing plate having a low degreeof polarization and a high transmittance is used for the absorbingpolarization selection member disposed at the reflective polarizationselection member side of the image display member, brightness and a highcontrast ratio of an image are balanced.

[0328] It should be noted that, although a case was described in thepresent example where a reflective liquid crystal display panel is used,a reflective display and a transmissive display may be used together bydisposing an opening portion in part of the pixel electrode functioningas the reflective member to partially transmit. In this case, a ¼phase-difference plate, a polarizing plate, and a lighting system may bedisposed at the undersurface of the reflective member. According to thisconfiguration, display of an image becomes possible, even in a situationin which the outside light is weak, such as at night or inside abuilding, by turning on the lighting system.

EXAMPLE 7

[0329] Another example of the invention will be described on the basisof the drawings.

[0330] A display device disposed with a function for switching to amirror status of Example 7 will be described using FIG. 37. Also, FIG.38 are pattern diagrams showing appearances of a mobile telephone inwhich the present display device is used, with FIG. 38(a) showing animage display status and FIG. 38(b) showing a mirror status. FIG. 39shows an example of a circuit configuration of the mobile telephoneshown in FIG. 38 and in which the present display device is used.

[0331] A mobile telephone 810 of Example 7 includes at least an antenna811, a speaker 812, buttons 814 such as a numeric keypad, a microphone815, a switching switch 813 of the mirror status and the image displaystatus, the image display portion 1000 of the present display device,and a mirror function portion 801.

[0332] The mobile telephone 810 of Example 7 is disposed with acommunications portion 10 for realizing telephone functions, anoperations portion 20 for inputting operations, and a display portion 30according to the invention that is capable of switching between aninformation display state and the mirror status. The communicationsportion 10 is disposed with a transmitting/receiving portion 821, whichis connected to the antenna 811 and implements thetransmission/reception of communications signals, a signal processingportion 822, which conducts the input and output of audio informationthrough the microphone 815 and the speaker 812 and implements signalconversion processing between the audio information and transmitted andreceived signals, and a communications control portion 823, whichcontrols the transmitting and receiving operations in response toinputted operation instructions. The operations portion 20 is disposedwith the numeric keypad/buttons 814 that conduct input of variousoperations, and the switching switch 813 for switching between theinformation display state and the mirror status.

[0333] The display portion 30 is disposed with the image display portion1000, which is disposed with a lighting system 836 and conductsinformation display, a display control portion 831, which receivescontrol instructions from the communications portion 10 and theoperations portion 20 and controls the operation of the display portion,a drive circuit portion 832, which drives the image display portion 1000in response to a control signal from the display control portion 831,the mirror function portion 801, which is superposed on the imagedisplay portion 1000 and selectively realizes the mirror status and atransmission state, an applied voltage generating portion 834, whichgenerates at least a voltage applied to the transmission polarizationaxis variable portion 400 of the mirror function portion 801, a mirrorcontrol portion 833, which controls the applied voltage generatingportion 834 so as to switch the state of the mirror function portion 801in response to a communications state or an instruction from theswitching switch 813, and a lighting switch 835 for turning the lightingsystem on and off in response to a control signal from the mirrorcontrol portion 833 and the display control portion 831.

[0334] As shown in FIG. 37, the present display device is one in whichthe area of the mirror function portion 801, which includes thereflective polarization selection member 300, the transmissionpolarization axis variable portion 400, and the absorbing polarizationselection member 500, has been made larger than the area of an imagedisplay region 1001 of the image display portion 1000. Aside from this,because the present display device basically includes the sameconfiguration and functions as those in Example 1, the same referencenumerals will be given to parts that are the same as those in theabove-described examples and detailed description will be omitted.

[0335] The reflective polarization selection member 300 of the mirrorfunction portion 801 is fixed, by a transparent adhesive, to a substrateconfiguring the transmission polarization axis variable portion 400. Aprojecting portion 801 a formed in a mobile telephone frame 810F is usedas a spacer and a constant space 801S is disposed between the mirrorfunction portion 801 and the image display portion 1000 so thatinterference patterns are not generated by the reflective polarizationselection member 300 halfway contacting the image display portion 1000.

[0336] Here, as described above, given that the primary purpose of thepresent display device during the mirror status is to reflect a viewer'sface for the viewer to view, and not to display information such as datathereon, it is preferable for the size of the mirror to be as describedabove, with a height of 58.6 mm and a width of 39.1 mm or more. However,because there are problems, such as power consumption increasing, whenthe image display portion is made large, the image display member cannotbe made too large. On the other hand, problems do not arise by makingthe area of the mirror function portion large. Thus, in Embodiment 7,the area of the mirror function portion is made as large as possible,regardless of the area of the image display region 1001.

[0337] Also, the mirror function portion 801 of the present displaydevice is one that can switch between an effectively transparent stateand the mirror status due to the control of the polarization state bythe transmission polarization axis variable portion 400. Therefore, in acase where the large area mirror function portion 801 is effectivelytransparent even if it is disposed with a design such as logo markhaving been administered, the degree of freedom of the design of thedevice is not robbed because the substrate is not affected.

[0338] Next, the operation of the mobile telephone 810 of the presentexample will be described with reference to FIG. 38.

[0339] As shown in FIG. 38(a), in the case where image display isconducted even when the mobile telephone is in use or standing by, themirror function portion 801 is effectively transparent, a bright imagedisplay is obtained, and logo marks and designs around the image displayportion are also visible. As shown in FIG. 38(b), in the case of themirror status, a mirror surface that is larger than the image displayportion appear s and a practical mirror is obtained.

[0340] It should be noted that operability is high because the displaydevice of Example 7 is configured so that switching between the mirrorstatus and the image display status can be done with one touch by theswitching switch 813. The switching switch 813 is configured so as to becapable of switching between a case where an alternating voltage ofabout ±3 V to ±5 V is applied to a pair of electrodes sandwiching theliquid crystal layer of the transmission polarization ax is variableportion 400 and a state in which the pair of electrodes is shorted.Moreover, in the case of the mirror status, power consumption is reducedby switching the image display portion 1000 to a non-display state andturning off the lighting system in conjunction with the switching switch813.

[0341] Also, by configuring the device so that the switching from themirror status to the image display status is automatically switched byan incoming call, convenience for the user is further improved becausethe incoming call information can be viewed without operating a switch.

[0342] It should be noted that no inconvenience is caused to the userbecause the switching of the mirror status and the image display statusis switched at a high speed within several +msec when a TN liquidcrystal element is used as the transmission polarization axis variableportion 400.

[0343] Also, although the area of the mirror function portion 801 ismade larger than the area of the image display region 1001 in thepresent example, in the present invention, the ratio between the area ofthe mirror function portion 801 or a region that can realize the mirrorstatus and the area of the image display region 1001 or atransmissive/reflective image display member is not limited to thisexample. of course, both areas maybe substantially the same, as in theabove-described examples. Alternatively, it is also possible to make thearea of the mirror function portion smaller, or superpose the mirrorfunction portion on the image display portion excluding a specificregion. For example, a configuration in which only the display portionof a mark that indicates whether or not the mobile telephone is in acommunicable state is not covered by the mirror function portion, sothat the mark can always be checked, can be made.

[0344] Moreover, although a case was described in the present examplewhere the entire surface of the mirror function portion was switched tothe mirror status, a configuration in which, for example, the mirrorregion of the mirror function portion is plurally divided and theswitching between the mirror status and the image display status isconducted per divided region can be made. More specifically, aconfiguration can be made in which the application of voltage to thetransmission polarization axis variable portion or the variableabsorbing polarization selection member is conducted per divided region,or in which pixel electrodes are disposed in a matrix and optionalpictures or characters in the mirror status are displayed.

EXAMPLE 8

[0345] Another example of the invention will be described on the basisof the drawings.

[0346] Example 8 of the invention will be described using FIGS. 40, 41and 42. In Example 8, the same reference numerals will be given toportions that are the same as those of Example 7, and detaileddescription will be omitted.

[0347] The configuration of Example 8 is a detachable mirror functionportion that enables a user to impart a mirror function to an existingmobile telephone. As shown in FIG. 41, the detachable mirror functionportion 801 includes the reflective polarization selection member 300,the transmission polarization axis variable portion 400, and theabsorbing polarization selection member 500, and these are mutuallyadhered and fixed by a transparent adhesive. Also, a transparentprotective member 500P comprising a film or a thin acrylic plate isadhered by a transparent adhesive on the surface of the absorbingpolarization selection member 500. A sponge-like, frame-like spacer 843having flexibility is disposed at a peripheral edge portion of thereflective polarization selection member 300, and a two-sided tape 844is disposed on the surface of the spacer 843 as needed. The spacer 843is disposed so that the reflective polarization selection member 300 canmaintain a constant space without contacting other members when themirror function portion is attached to a device such as a mobiletelephone. Thus, interference fringe caused by the reflectivepolarization selection member 300 contacting other members is prevented.

[0348] The transmission polarization variable portion 400 is connectedto a mirror function drive portion 840 via wiring connected to thetransparent electrodes formed on in transparent substrate shapesconfiguring this.

[0349] As shown in FIG. 42, the mirror function drive portion 840 isconfigured by a power source 845 comprising a small battery, a switchingswitch 846, and a drive circuit 847 that generates a voltage that drivesthe transmission polarization axis variable portion 400 by power supplyfrom the power source 845, and drives the transmission polarization axisvariable portion 400 by operation of the switching switch 846 to switchthe mirror function portion between the mirror status and thetransparent state.

[0350] When the mirror function portion 801 is attached to the mobiletelephone 810, the wiring between the mirror function portion 801 andthe mirror function drive portion 840 can be configured so that it isattached through a strap attachment portion 841 of the mobile telephoneand wiring 842 and the mirror function drive portion 840 are like astrap. In this case, there is the advantage that, even if the mirrorfunction drive portion 840 is accidentally pulled, the force thereof isstopped by the strap attachment portion 841 of the mobile telephone andis not directly added to the mirror function portion.

EXAMPLE 9

[0351] A display device of Example 9 of the invention will be describedon the basis of FIG. 43.

[0352] The display device of Example 9 of FIG. 43 uses an organicelectroluminescence (EL: electro luminescence) display panel 900 as animage display portion emitting the image light, and the same referencenumerals will be given to members that are the same as those of Example1, and detailed description will be omitted.

[0353] The present display device is configured by the organic ELdisplay panel 900 that emits image light of the first linearpolarization, the reflective polarization selection member 300, thetransmission polarization axis variable portion 400, and the absorbingpolarization selection member 500. The absorbing polarization selectionmember 208 and phase-difference plate 901, which transmit the firstlinear polarization component and absorb the second linear polarizationcomponent, whose polarization axis is orthogonal to that of the firstlinear polarization component, are disposed at the side of the organicEL display panel 900 facing the reflective polarization selection member300.

[0354] A ¼ wavelength plate may be used as the phase-difference plate901. For example, a polymer film such as uniaxially stretchedpolycarbonate, polysulfone, or polyvinyl alcohol can be used. Althoughit is difficult to configure a phase-difference plate functioning as a ¼wavelength plate with respect to the entire visible wavelength regionwith one type of phase-difference plate due to wavelength dependency(below, wavelength dispersion) of the refractive index of materialscommonly configuring the ¼ wavelength plate , a plate configured tofunction as a ¼ wavelength plate in a wide wavelength region by adheringtogether at least two types of phase-difference plates whose wavelengthdispersion is different so that the optical axes thereof are orthogonalcan be used.

[0355] The organic EL display panel 900 is a self-luminous displaydevice that converts electric energy to light energy by injecting acurrent to an emission layer comprising an organic thin film and emitsthe light energy, and has a configuration in which a transparentelectrode 903 comprising ITO, a hole transport layer 904, an emissionlayer 907, an electron transport layer 906, and a reflective metalelectrode 905 configured by Al or the like are successively laminated onthe transparent substrate 902. These laminated films are sealed by asealing agent 908 between the transparent substrate 902 and a sealmember 909 in a state in which oxygen and water have been removed inorder to suppress deterioration.

[0356] It is thought that, in an organic EL display panel, when a DCvoltage is applied between the transparent electrode 903, which is ananode, and the reflective metal electrode 905, which is a cathode, thehole injected from the transparent electrode 903 passes through the holetransport layer 904 and electrons injected from the cathode (reflectivemetal electrode) 905 pass through the electron transport layer, so thatthey respectively reach the emission layer 907, recombination of theelectrons/hole is generated, and an emission of a predeterminedwavelength is generated. Because the light emitted from the emissionlayer 907 is usually omnidirectionally and isotropically emitted withoutdirectivity, it is preferable to use a metal electrode or an electrodematerial having high reflectance in order to effectively use the lightprocessing to the metal electrode 905 as display light.

[0357] The configuration of the organic EL display panel 900 is notlimited to the above-described configuration. In other words, aself-luminous display device that is configured by at least an emissionlayer and a reflective member disposed at the undersurface of theemission layer can be used as the organic EL display panel pertaining tothe invention.

[0358] Next, the operation of the display device of Example 9 will bedescribed using FIG. 43. The right side of FIG. 43 shows the imagedisplay status and the left side of FIG. 43 shows the mirror status.

[0359] When the display device is in the image display status, thetransmission polarization axis variable portion 400 is switched to astate in which voltage is not applied to the liquid crystal layer 407configuring this, i.e., an OFF state. In the case of the image displaystatus, light emitted from the emission layer is directly emitted fromthe transparent substrate 902 or emitted from the transparent substrate902 after being reflected by the undersurface metal electrode 905.

[0360] When image light 3201 emitted from the transparent substrate 902is transmitted through the phase-difference plate 901 and passes throughthe absorbing polarization selection member 208, the first linearpolarization component is transmitted and the second linear polarizationcomponent, whose polarization axis is orthogonal to that of the firstlinear polarization component, is absorbed. The image light 3201transmitted through the absorbing polarization selection member 208 isalso transmitted through the reflective polarization selection member300 and made incident at the transmission polarization axis variableportion 400. In this case, the image light 3201 passing through thetransmission polarization axis variable portion 400 is changed from thefirst linear polarization to the second linear polarization. The imagelight 3201 transmitted through the transmission polarization axisvariable portion 400 is made incident at the absorbing polarizationselection member 500. Because the absorbing polarization selectionmember 500 absorbs the first linear polarization component and transmitsthe second linear polarization component, the image light 3201 that ischanged to the second linearly polarized light by the transmissionpolarization axis variable portion 400 is transmitted through theabsorbing polarization selection member 500 and viewed by a viewer 2000.

[0361] Although outside light 3202 made incident at the display devicefrom the viewer 2000 side is non-polarized light, when it is transmittedthrough the absorbing polarization selection member 500, the firstlinear polarization component is absorbed and only the second linearpolarization component is transmitted. When the outside light 3202transmitted through the absorbing polarization selection member 500 istransmitted through the transmission polarization axis. variable portion400, it is changed from the second linearly polarized light to the firstlinearly polarized light, transmitted through the reflectivepolarization selection member 300, and made incident at the organic ELdisplay panel 900.

[0362] When the outside light 3202 made incident at the organic ELdisplay panel 900 is transmitted through the absorbing polarizationselection member 208 and transmitted through the phase-difference plate901, it receives the action thereof and becomes a circular polarization(here, for example, a clockwise circular polarization). When the outsidelight 3202 transmitted through the phase-difference plate 901 isreflected by the metal electrode 905, it becomes a circular polarizationin which the phase is π offset and the rotational direction is reversed(a counterclockwise circular polarization). When the outside light 3202reflected by the metal electrode 905 is again transmitted through thephase-difference plate 901, it receives the action thereof, this timebecomes the second linear polarization, and is absorbed by the absorbingpolarization selection member 208, whereby it does not return to theviewer 2000 side.

[0363] Therefore, in the image display status, a bright image can beobtained because the image light 3201 emitted from the organic ELdisplay panel 900 proceeds toward the viewer with virtually no loss.Moreover, because the outside light 3202 made incident at the displaydevice from the surrounding area is not reflected by the reflectivepolarization selection member 300 functioning as a mirror in the case ofthe mirror status, and because the light reflected by the metalelectrode 905 of the organic EL display panel 900 is absorbed by theabsorbing polarization selection member 208, it is virtually notviewable to the viewer 2000. In other words, an image display having ahigh contrast ratio and in which unnecessary reflection of outside lightis suppressed can be realized.

[0364] When the display device is switched to the mirror status, thetransmission polarization axis variable portion 400 is switched to an ONstate by applying an electric field to the liquid crystal layer 407configuring this. In the case of the mirror status, although outsidelight 3203 proceeding toward the display device from the viewer 2000side is non-polarized light, when it is transmitted through theabsorbing polarization selection member 500, the first linearpolarization component is absorbed and only the second linearpolarization component is transmitted and made incident at thetransmission polarization axis variable portion 400. At this time, theoutside light 3203 made incident at the transmission polarization axisvariable portion 400 is transmitted through the transmissionpolarization axis variable portion 400 as the second linearly polarizedlight without its polarization axis being changed, and reaches thereflective polarization selection member 300. At the reflectivepolarization selection member 300, because the first linear polarizationcomponent is transmitted and the second linear polarization component ismirror-reflected, the outside light 3203 is reflected by the reflectivepolarization selection member 300. The outside light 3203 reflected bythe reflective polarization selection member 300 is transmitted throughthe transmission polarization axis variable portion 400 as the secondlinear polarization without its polarization axis being changed, is alsotransmitted through the polarization selection member 500 and proceedstoward the viewer, whereby the mirror status is realized.

[0365] At this time, it is preferable to switch the display region ofthe organic EL display panel 900 corresponding to the region serving asthe mirror status to a non-emitting state at the same time as theoperation of the mirror function. Because leakage of light from anundersurface side of the reflective polarization selection member 300can be completely eliminated by this operation, a high-definition mirrorthat reflects a reflection image of a high contrast ratio can berealized, and power consumption of the display device is reduced by theamount that the emission amount is suppressed.

[0366] However, the display region does not always have to be switchedto a non-emitting state. Even when the image light is emitted from theorganic EL display panel 900, because the image light emitted from theorganic EL display panel 900 is the first linearly polarized lighttransmitted through the absorbing polarization selection member 208, itis transmitted through the reflective polarization selection member 300,transmitted through the transmission polarization axis variable portion400 as the first linearly polarized light without its polarization axisbeing changed, absorbed by the absorbing polarization selection member500, and is virtually not viewable to the viewer 2000. Thus, a mirrorthat reflects a reflection image of a high contrast ratio can berealized.

[0367] It should be noted that the characteristics of the polarizingplates functioning as the absorbing polarization selection member 208and the absorbing polarization selection member 500 are directly relatedto the image quality of the image display status and the ease with whichthe mirror of the mirror status can be viewed. For this reason, similarto Example 1, it is effective to use a polarizing plate having a highdegree of polarization for one of the absorbing polarization selectionmember 208 and the absorbing polarization selection member 500 and touse a polarizing plate having a low degree of polarization for the otherin order to maintain a sufficient contrast ratio and to improveluminance in the image display status.

[0368] As described above in each of the examples, according to thedisplay device of the present invention, because the reflectivepolarization selection member functioning as the mirror can beoptionally switched between an effectively transparent state and a statefunctioning as the mirror, there is the effect that the switchingbetween the image display status and the mirror status can be realizedwithout deteriorating their mutual performance. In other words, in theimage display status, a bright image is obtained with virtually no lossof image light, and a high-definition image, in which there is nodeterioration of image quality resulting from outside light such asglare and a drop in contrast ratio accompanying glare, is obtained evenin an environment in which the surrounding area is bright.

[0369] In the mirror status, there is the effect that a bright mirrorcan be realized because outside light is effectively reflected, andbecause leakage of light of the image light is suppressed, a mirror thatreflects a reflection image having a high contrast ratio can berealized. Therefore, in the mirror status, an easy-to-view reflectionimage suitable for a person to view his/her own face or figure isobtained.

[0370] As described above, according to the invention, there can beprovided a device that is capable of switching between a state in whicha high-quality image is displayed and a mirror status in which isobtained an easy-to-view reflection image suitable for a person to viewhis/her own face or figure.

What is claimed is:
 1. A device capable of switching between an imagedisplay status and a mirror status, the device including an imagedisplay portion that emits image light for displaying a desired imageand a mirror function portion that is superposed on the image displayportion and is capable of being switched between an image transmittancestate that transmits the image light and a mirror status that reflectsoutside light, the mirror function portion including reflectivepolarization selection means, transmission polarization axis variablemeans, and absorbing polarization selection means successively disposedfrom the image display portion side, with the reflective polarizationselection means transmitting a first polarization of a predeterminedpolarization axis and reflecting a second polarization whosepolarization axis intersects that of the first polarization, thetransmission polarization axis variable means being capable of switchingbetween a state that transmits by changing the incident firstpolarization to the second polarization and a state that transmitswithout changing the polarization axis of the incident light, and theabsorbing polarization selection means transmitting one of the firstpolarization and the second polarization and absorbing the other, andthe image display portion being disposed with image light-usepolarization selection means that transmits the first polarization andabsorbs the second polarization, the image display portion emitting, asthe image light, the first polarization transmitted through the imagelight-use polarization selection means.
 2. The device of claim 1,further including switching means for switching the mirror functionportion between the image transmittance state and the mirror status,wherein the switching means switches the mirror function portion to theimage transmittance state by switching the transmission polarizationaxis variable means to a state that changes the first polarization tothe second polarization and switches the mirror function portion to themirror status by switching the transmission polarization axis variablemeans to a state that transmits without changing the incidentpolarization axis.
 3. The device of claim 1, further including switchingmeans for switching the mirror function portion between the imagetransmittance state and the mirror status, wherein the switching meansswitches the mirror function portion to the image transmittance state byswitching the transmission polarization axis variable means to a statethat transmits without changing the incident polarization axis andswitches the mirror function portion to the mirror status by switchingthe transmission polarization axis variable means to a state thatchanges the first polarization to the second polarization.
 4. A devicecapable of switching between an image display status and a mirrorstatus, the device including an image display portion that emits imagelight for displaying a desired image and a mirror function portion thatis superposed on the image display portion and is capable of beingswitched between an image transmittance state that transmits the imagelight and a mirror status that reflects outside light, the mirrorfunction portion including first reflective polarization selectionmeans, transmission polarization axis variable means, second reflectivepolarization selection means, and variable polarization selection meanssuccessively disposed from the image display portion side, with thefirst reflective polarization selection means transmitting a firstpolarization of a predetermined polarization axis and reflecting asecond polarization whose polarization axis intersects that of the firstpolarization, the transmission polarization axis variable means beingcapable of switching between a state that transmits by changing theincident first polarization to the second polarization and a state thattransmits without changing the polarization axis of the incident light,the second reflective polarization selection means reflecting one of thefirst polarization and the second polarization and transmitting theother, and the variable polarization selection means being capable ofswitching between a state that absorbs one of the first polarization andthe second polarization and transmits the other and a state thattransmits all polarization components, and the image display portionbeing disposed with image light-use polarization selection means thattransmits the first polarization and absorbs the second polarization,the image display portion emitting, as the image light, the firstpolarization transmitted through the image light-use polarizationselection means.
 5. The device of claim 4, further including switchingmeans for switching the mirror function portion between the imagetransmittance state and the mirror status, wherein the switching meansswitches the mirror function portion to the image transmittance state byswitching the transmission polarization axis variable means to a statethat changes the first polarization to the second polarization andswitching the variable polarization selection means to a state thatabsorbs the first polarization and transmits the second polarization andswitches the mirror function portion to the mirror status by switchingthe transmission polarization axis variable means to a state thattransmits without changing the incident polarization axis and switchingthe variable polarization selection means to a state that transmits allof the polarization components.
 6. The device of claim 4, furtherincluding switching means for switching the mirror function portionbetween the image transmittance state and the mirror status, wherein theswitching means switches the mirror function portion to the imagetransmittance state by switching the transmission polarization axisvariable means to a state that transmits without changing the incidentpolarization axis and switching the variable polarization selectionmeans to a state that absorbs the second polarization and transmits thefirst polarization and switches the mirror function portion to themirror status by switching the transmission polarization axis variablemeans to a state that changes the first polarization to the secondpolarization and switching the variable polarization selection means toa state that transmits all of the polarization components.
 7. A devicecapable of switching between an image display status and a mirrorstatus, the device including an image display portion that emits imagelight for displaying a desired image and a mirror function portion thatis superposed on the image display portion and is capable of beingswitched between an image transmittance state that transmits the imagelight and a mirror status that reflects outside light, the mirrorfunction portion including first reflective polarization selectionmeans, transmission polarization axis variable means, and secondreflective polarization select ion means successively disposed from theimage display portion side, with the first reflective polarizationselection means transmitting a first polarization of a predeterminedpolarization axis and reflecting a second polarization whosepolarization axis intersects that of the first polarization, thetransmission polarization axis variable means being capable of switchingbetween a state that transmits by changing the incident firstpolarization to the second polarization to transmit the secondpolarization and a state that transmits without change the polarizationaxis of the incident light, and the second reflective polarizationselection means reflecting one of the first polarization and the secondpolarization and transmitting the other, and the image display portionbeing disposed with image light-use polarization selection means thattransmits the first polarization and absorbs the second polarization,the image display portion emitting, as the image light, the firstpolarization transmitted through the image light-use polarizationselection means.
 8. The device of claim 2, 3, 5 or 6, wherein the imagedisplay portion is capable of being switched to a state in which theimage light is not emitted, and when the switching means switches themirror function portion to the mirror status, the switching meansswitches, in conjunction therewith, the image display portion to thestate in which the image light is not emitted.
 9. The device of claim 8,wherein the image display portion includes a lighting system and aliquid crystal element, and the switching means turns the lightingsystem off or switches the liquid crystal element to a dark display inorder to switch the image display portion to the state in which theimage light is not emitted.
 10. The device of claim 8, wherein thetransmission polarization axis variable means has a configuration thatis capable of being switched to a state that transmits only through apartial region without changing the incident polarization axis, and theswitching means switches a display of the image display portion of aportion overlapping with the partial region to a dark display when thetransmission polarization axis variable means is switched to the statethat transmits only through the partial region without changing theincident polarization axis and the image light is not emitted from thepartial region.
 11. The device of claim 1, 4 or 7, wherein thetransmission polarization axis variable means includes a liquid crystallayer and an electrode for applying an electric field in a thicknessdirection of the liquid crystal layer, the liquid crystal layer having aconfiguration in which a long axis direction of liquid crystal moleculesis continuously twisted 90° in the thickness direction when the electricfield is not applied and in which the long axis direction of the liquidcrystal molecules becomes parallel to the thickness direction when theelectric field is applied, and, when the mirror function portion is inthe mirror status, the transmission polarization axis variable means isin a state that applies the electric field to the liquid crystal layer.12. The device of claim 1, 4 or 7, wherein the transmission polarizationaxis variable means includes a liquid crystal layer and an electrode forapplying an electric field in a thickness direction of the liquidcrystal layer, the liquid crystal layer having a configuration in whicha long axis direction of liquid crystal molecules is continuouslytwisted 90° in the thickness direction when the electric field is notapplied and in which the long axis direction of the liquid crystalmolecules becomes parallel to the thickness direction when the electricfield is applied, and, when the mirror function portion is in the mirrorstatus, the transmission polarization axis variable means is in a statethat does not apply the electric field to the liquid crystal layer. 13.The device of claim 1, wherein, when P1 represents the degree ofpolarization of the image light-use polarization selection means and P2represents the degree of polarization of the absorbing polarizationselection means, the relationship of 0.966≦P1≦0.995≦P2 is satisfied. 14.The device of claim 1, wherein, when P1 represents the degree ofpolarization of the image light-use polarization selection means and P2represents the degree of polarization of the absorbing polarizationselection means, the relationship of 0.966≦P2≦0.995≦P1 is satisfied, andwhen the mirror function portion is switched to the mirror status, theimage display portion is switched, in conjunction therewith, to a statein which the image light is not emitted.
 15. The device of claim 4 or 7,wherein the first reflective polarization selection means is disposed sothat an interval between the first reflective polarization selectionmeans and the second reflective polarization selection means is 0.11 mmor less.
 16. The device of claim 1, 4 or 7, wherein a size of a regionserving as the mirror status of the mirror function portion is at least58.6 mm×39.1 mm.
 17. The device of claim 1, wherein the image displayportion includes an organic electroluminescence display element, with aphase-difference plate and the image light-use polarization selectionmeans being disposed between an emission layer of the organicelectroluminescence display element and the reflective polarizationselection means.
 18. A display device disposed with an image displayportion that emits light including a first polarization state and amirror function portion that is superposed on the image display portionand is capable of selecting between one of an image display status thattransmits image light from the image display member and a mirror statusthat reflects light proceeding from the outside to the image displaymember, wherein, when the mirror function portion is switched to themirror status, an emission state of the image display member is switchedto a non-emission state in conjunction therewith.
 19. The display deviceof claim 18, wherein the image display portion includes a pair oftransparent substrates joined with a constant gap therebetween, a liquidcrystal layer sandwiched between the transparent substrates, a pixelelectrode group disposed in a matrix formed by a transparent electrodeon at least one of the pair of transparent substrates, display-usepolarization selection means that is disposed at a viewing side of theliquid crystal layer, transmits the first linear polarization component,and absorbs the second linear polarization component, a polarizing platedisposed at an undersurface side of the liquid crystal layer, and alighting system disposed at a rear surface thereof, and the switchingmeans turns the lighting system off when the mirror function portion isin the mirror status.
 20. The display device of claim 18, wherein theimage display portion includes a pair of transparent substrates joinedwith a constant gap therebetween, a liquid crystal layer sandwichedbetween the transparent substrates, a pixel electrode group disposed ina matrix formed by a transparent electrode on at least one of the pairof transparent substrates, display-use polarization selection means thatis disposed at a viewing side of the liquid crystal layer, transmits thefirst linear polarization component, and absorbs the second linearpolarization component, a polarizing plate disposed at an undersurfaceside of the liquid crystal layer, and a lighting system disposed at arear surface thereof, and the switching means switches the liquidcrystal layer of a region of the image display member overlapping with aregion of the mirror status to a dark display when the mirror functionportion is in the mirror status.
 21. An instrument disposed with adisplay device, the display device including an image display portionthat emits image light for displaying a desired image and a mirrorfunction portion that is superposed on the image display portion and iscapable of being switched between an image transmittance state thattransmits the image light and a mirror status that reflects outsidelight, the mirror function portion including reflective polarizationselection means, transmission polarization axis variable means, andabsorbing polarization selection means successively disposed from theimage display portion side, with the reflective polarization selectionmeans transmitting a first polarization of a predetermined polarizationaxis and reflecting a second polarization whose polarization axisintersects that of the first polarization, the transmission polarizationaxis variable means being capable of switching between a state thattransmits by changing the incident first polarization to the secondpolarization and a state that transmits without changing thepolarization axis of the incident light, and the absorbing polarizationselection means transmitting one of the first polarization and absorbingthe second polarization and the image display portion being disposedwith image light-use polarization selection means that transmits thefirst polarization and absorbs the second polarization, the imagedisplay portion emitting, as the image light, the first polarizationtransmitted through the image light-use polarization selection means.22. A device capable of switching between an image display status and amirror status, the device including an image display portion that emitsimage light for displaying a desired color image and a switchingfunction portion superposed on the image display portion, the switchingfunction portion being capable of switching between a state thattransmits the image light of the image display portion to the outsideand displays a color image at the outside and a state that changesincident outside light to a polarization state reflected on the imagedisplay portion in order to switch the image display portion to themirror status, the switching function portion including transmissionpolarization axis variable means and absorbing polarization selectionmeans successively disposed from the image display portion side, withthe transmission polarization axis variable means having a configurationthat is capable of switching between a state that transmits by changing,when a first polarization of a predetermined polarization axis is madeincident thereat, the first polarization to a second polarization whosepolarization axis intersects that of the first polarization and a statethat transmits without changing the polarization axis of the incidentlight, and the absorbing polarization selection means transmitting oneof the first polarization and the second polarization and absorbing theother, the image display portion having a configuration that conductscolor display by a field-sequential color display system, and the imagedisplay portion including reflective polarization selection means thattransmits the first polarization and reflects the second polarization,with the image display portion generating the image light of a color ofthe first polarization by the first polarization being transmittedthrough the reflective polarization selection means.